C_HOSTS_Obe_Par – Blackman & Eastop's Aphids on the World's Plants

*Oberna*	Caryophyllaceae
*Oberna behen* = Silene vulgaris
*O. multifida*	Macrosiphum eastopi, stellariae
*O. wallichiana*	Aphidura ornatella; Aphis craccivora; Brachycolus cucubali

Use key to apterae on Silene.

Obione see Atriplex

Amaranthaceae

*Ochetophila*	Rhamnaceae
*Ochetophila nana*	Aphis conflicta
O. *trinervis*	Aphis conflicta

*Ochna*	Ochnaceae
A single aphid species, Sitobion ochnearum, is recorded from 4 spp. of Ochna; O. afzelii, O. leptoclada, O. pretoriensis, O. pulchra.

*Ochradenus*	Resedaceae
*Ochradenus baccatus*	Myzus persicae

*Ochroma*	Bombacaceae
*Ochroma lagopus*	Aphis gossypii

*Ochthodium*	Brassicaceae
*Ochthodium aegyptiacum*	Brevicoryne brassicae

*Ocimum*	Lamiaceae
*Ocimum americanum*	Aphis gossypii
*O. basilicum*	Aphis [affinis], craccivora, fabae, gossypii; Aulacorthum solani; Macrosiphum mesosphaeri; Myzus ornatus, persicae; Neomyzus circumflexus; [Ovatus crataegarius]; Sitobion colei
*O. canum* = O. americanum
*O. gratissimum*	Aphis gossypii; Aulacorthum solani; Macrosiphum mesosphaeri, salviae; Myzus ornatus
*O. minimum*	Myzus ornatus
*O. obovatum*	Aphis gossypii
*O. sanctum* = O. tenuiflorum
*O. tenuiflorum*	Aphis gossypii; Macrosiphum mesosphaeri; Myzus ornatus
*O. urticifolium* = O. gratissimum
*Ocimum* sp.	Aphis spiraecola; [Sitobion indicum]

Key to apterae on Ocimum:-

1	SIPH mainly or wholly dark, with a subapical zone of reticulation (at least 4-5 rows of closed polygonal cells)	…..2
–	SIPH pale or dark, without subapical polygonal reticulation	…..go to key to polyphagous aphids
2	ANT and tibiae mainly pale. Dorsum with an extensive solid dark shield across ABD TERG 1-5, fused with marginal and antesiphuncular sclerites. Longest hairs on ANT III less than 0.5 × BD III	…..Sitobion colei
–	ANT and tibiae mainly dark. Dorsum without a complete dark shield, with or without a less extensive dark patch. Longest hairs on ANT III more than 0.5 × BD III	…..3
3	Dorsal abdomen with a central dark patch. Head as dark as ANT. SIPH wholly dark. Process at base of prothoracic furca is tubercular, about as long as its basal width	…..Macrosiphum salviae
–	Dorsal abdomen without a dark central patch. Head paler than ANT. SIPH usually with paler basal section. Process at base of prothoracic furca is broadly conical, much shorter than its basal width	…..Macrosiphum mesosphaeri

*Ocotea*	Lauraceae
*Ocotea acutifolia*	Lizerius ocoteae
*O. glomerata* (?)	Lizerius pustulatus
O. porphyria	Lizerius ocoteae
*Ocotea* sp.	Aphis (Toxoptera) aurantii; Lizerius tuberculatus

Key to species:-

1	Body of aptera with conical, club-shaped or crown-shaped processes	…..2
–	Body of aptera without processes	…..go to key to polyphagous aphids
2	ABD TERG 1-5 each with 6 sclerites, the marginal ones developed into short conical processes, and transverse bars on ABD TERG 6-8; ABD TERG 8 bearing 2 large conical processes and 2-4 much smaller ones (fig. 63A). Antenna of aptera 6-segmented	…..Lizerius ocoteae
–	Dorsal body membranous, with numerous short spinulose club-shaped or crown-shaped processes. ABD TERG 8 with 4 tapering or finger-like processes (e.g. fig. 63B). Antennae of aptera often 5-segmented	…..3
3	Aptera with apical diameter of largest spinal process on ABD TERG V c. 30 μm, about as wide as SIPH pore. Processes are finger-like/tapering only on ABD TERG 8. Alata with ANT III bearing 8-17 secondary rhinaria in a row, and ANT PT/BASE 0.18-0.29	…..Lizerius tuberculatus
–	Aptera with apical diameter of largest spinal process on ABD TERG V c. 20 μm, about 0.5 of width of SIPH pore. Marginal processes are finger-like/tapering on ABD TERG (4-)5-7. Alata with ANT III bearing 15-26 secondary rhinaria scattered all over segment, and ANT PT/BASE 0.30-0.36	…..Lizerius pustulatus

Octadesmia see Dilomilis

Orchidaceae

Octomeron see Platostoma

Lamiaceae

Ocymum see Ocimum

Lamiaceae

*×Odontioda*	Orchidaceae
×*Odontioda* sp. (hybrid)	Aphis spiraecola

*Odontites* (including Orthantha)	Orobanchaceae
*Odontites lutea*	Brachycaudus mimeuri, persicae
*O. purpureus*	Brachycaudus helichrysi
*O. serotina* = O. vulgaris
*O. sicula*	Brachycaudus mimeuri
*O. verna*	Brachycaudus mimeuri
*O. vulgaris*	Aphis frangulae, sibirica; Brachycaudus persicae

Key to apterae on Odontites:-

1	Cauda short and rounded, not longer than its basal width	…..2
–	Cauda finger-like, longer than its basal width	…..3
2	Dorsum with an extensive solid black shield covering almost all of metanotum and ABD TERG 1-6	…..Brachycaudus mimeuri (or persicae: see text)
–	Dorsum without an extensive solid black shield	…..Brachycaudus helichrysi
3	SIPH 0.4-0.9 × cauda, which is as dark as SIPH and bears 7-19 hairs	…..Aphis sibirica
–	SIPH (0.8-)0.9-2.1 × cauda, which is usually paler than SIPH and bears 4-11(-13) hairs	….Aphis frangulae group (or try key to polyphagous aphids)

*Odontoglossum*	Orchidaceae
*Odontoglossum* sp.	Sitobion luteum

(or try key to orchid-feeding aphids under Cymbidium)

*Odontonema*	Acanthaceae
*Odontonema strictum*	Myzus persicae

Odontospermum see Asteriscus

Asteraceae

*Oedibasis*	Apiaceae
*Oedibasis platycarpa*	Aphis craccivora

*Oemleria* (including Osmaronia)	Rosaceae
*Oemleria cerasiformis*	Macrosiphum [euphorbiae], occidentale, osmaroniae

Key to apterae on Oemleria:-

–	R IV +V short and blunt, about as long as its basal width, 0.7-0.8 × HT II. ANT BASE VI 1.5-2.3 × R IV+V. Cauda with 8-14 hairs	….. Macrosiphum occidentale
–	R IV+V much longer than its basal width, 0.9-1.1 × HT II. ANT BASE VI 1.0-1.5 × R IV+V. Cauda with 5-8 hairs	….. Macrosiphum osmaroniae

*Oenanthe*	Apiaceae
*Oenanthe aquatica*	Anuraphis subterranea; Aulacorthum solani; Cavariella aegopodii; Pemphigus protospirae
*Oe. crocata*	Aphis fabae; Cavariella aegopodii, pastinacae, theobaldi; Hyadaphis passerinii; Macrosiphum euphorbiae; Myzus persicae
*Oe. javanica*	Amphorophora cryptotaeniae; Aphis craccivora, gossypii, spiraecola; Brachycaudus helichrysi; Cavariella oenanthi, salicicola; [Hyalopterus pruni]; Myzus persicae; Semiaphis heraclei
*Oe. pimpinelloides*	Aphis fabae, spiraecola; Dysaphis apiifolia; Hyadaphis passerinii
*Oe. sarmentosa*	Cavariella aegopodii, konoi; Hyadaphis passerinii; Pemphigus populicaulis
*Oe. silaifolia*	Cavariella aegopodii; Macrosiphum euphorbiae
*Oe. stolonifera* = Oe. javanica
*Oenanthe* spp.	[Aphis oenanthis Lichtenstein (nomen nudum)]; Cavariella salicis

Key to apterae on Oenanthe:-

1	ABD TERG 8 with a posteriorly projecting process above cauda bearing 2 hairs (e.g. Fig 10g); in 1 species (Cavariella oenanthi) this is reduced to a small warty knob in the centre of ABD TERG 8, with 2 associated hairs (Fig. 10i)	…..2
–	No supracaudal process, nor are there 2 hairs on ABD TERG 8 close together and associated with a warty knob	…..8
2	SIPH clavate; swollen on distal half to at least 1.2 × narrowest part of basal half. ANT PT/BASE 0.6-2.0	…..3
–	SIPH tapering or cylindrical, or with slight subapical swelling. ANT PT/BASE 1.3-3.5	.….6
3	Supracaudal process conical or finger-like, not projecting to tip of cauda	…..4
–	Supracaudal process large, conical, extending beyond and usually covering cauda	…..6
4	ANT PT/BASE 2.6-4.0	…..Cavariella pastinacae
–	ANT PT/BASE 0.6-2.0	…..5
5	ANT PT/BASE 0.6-1.3. R IV+V 0.7-0.95 × HT II, and without accessory hairs	.….Cavariella aegopodii
–	ANT PT/BASE 1.35-2.0. R IV+V 1.0-1.2 × HT II, with 2 accessory hairs	…..Cavariella konoi
6	R IV+V 1.05-1.2 × HT II. SIPH short and stout, narrowing only at base	…..Cavariella salicicola
–	R IV+V 0.85-1.04 × HT II. SIPH with narrower basal stem extending over about 0.3 of length	…..Cavariella salicis
7	Supracaudal process reduced to a warty knob, distinctly shorter than ANT II (Fig. 10i). Head and Cauda dark, tergum with variably developed dark markings. Secondary rhinaria sometimes present on ANT III-V or IV-V (of aptera). ANT PT/BASE 1.3-1.8. Femoral hairs numerous, long and fine, longer than 0.5 × width of hind femur	…..Cavariella oenanthi
–	Supracaudal process at least as long as ANT II. Head and cauda pale, tergum without dark markings. Antennae (of aptera) without secondary rhinaria. ANT PT/BASE 2.1-3.5. Femoral hairs sparse and shorter than 0.5 × width of hind femur	…..Cavariella theobaldi
8	SIPH very small and flangeless; less than 0.5 × cauda and often not much longer (1.0-1.8 ×) than their diameter at midlength	…..Semiaphis heraclei
–	SIPH (if present at all) more than 0.6 × cauda, and with a flange	…..9
9	Cauda helmet-shaped, a little shorter than its basal width. Spinal tubercles (STu) present on head and at least ABD TERG 8	…..10
–	Cauda (if developed at all) tongue- or finger-shaped and distinctly longer than its basal width. STu usually not evident	…..11
10	SIPH less than 2 × basal width with close-set rows of spinules. Cauda with c.10-12 hairs	…..Anuraphis subterranea
–	SIPH more than 2 × basal width with normal imbrication. Cauda with 5 hairs	…..Dysaphis apiifolia
11	SIPH and cauda both dark, with SIPH swollen on distal 0.7, and 0.9-1.4 × cauda	…..Hyadaphis passerinii
–	Without that combination of characters	…..12
12	SIPH strongly clavate, with swollen part maximally 1.8-2.1 × minimum width on basal part, and with a subapical constriction bearing 2-3 rows of tranverse striae below the well-developed flange. R IV+V 1.5-1.7 × HT II. Apex of ANT PT pointed	…..Amphorophora cryptotaeniae
–	Without that combination of characters	…..go to key to polyphagous aphids

*Oenocarpus*	Arecaceae
*Oenocarpus distichus*	Cerataphis brasiliensis

*Oenothera*	Onagraceae
*Oenothera affinis*	Aphis oenotherae
*Oe. amoena* = Clarkia amoena
*Oe. berteroana* = Oenothera affinis
*Oe. biennis*	Anoecia [cornicola], oenotherae, [setariae]; Aphis fabae, frangulae, gossypii, grossulariae, holoenotherae, nasturtii, oenotherae, oestlundi; Aulacorthum solani; Brachycaudus cardui; Macrosiphum euphorbiae, gaurae, [pallidum]; Myzus [biennis], oenotherae, persicae; [Pemphigus oenotherae (nomen nudum)]; [Uroleucon ambrosiae]
*Oe. brevihypanthialis* = Oe. deflexa var. brevihypanthialis
*Oe. casimiri*	Aphis holoenotherae
*Oe. cespitosa* = Pachylophis cespitosa
*Oe. deflexa* (incl. var. brevihypanthialis)	Aphis holoenotherae
*Oe. erythrosepala* = Oenothera glazioviana
*Oe. flaemingina*	[Aphis sp. nr. holoenotherae – Rakauskas 2008]
*Oe. flava*	[Protaphis middletonii]
*Oe. fruticosa* = Kneiffia fruticosa
*Oe. glazioviana*	Aphis epilobiaria, oenotherae, spiraecola; [Macrosiphum rosae]; Myzus ornatus; [Uroleucon nigrotuberculatum]
*Oe. grandiflora* = Oenothera glazioviana
*Oe. hazelae* var. subterminalis	Aphis holoenotherae
*Oe. javanica*	Aphis spiraecola
*Oe. lamarckiana*	Aphis holoenotherae, oenotherae
*Oe. megallanica*	Aphis grossulariae
*Oe. missouriensis* = Megapterium missouriense
*Oe. muricata* = Oenothera biennis
*Oe. oakesiana*	Aphis holoenotherae, oenotherae
*Oe. odorata*	Aphis gossypii, oenotherae, spiraecola; Rhopalosiphoninus staphyleae
*Oe. parviflora*	Aphis oenotherae
*Oe. perangusta × biennis*	Aphis holoenotherae
*Oe. picensis*	Aphis spiraecola
*Oe. pilosella* = Kneiffia pilosella
*Oe. rosea*	Rhopalosiphoninus staphyleae
*Oe. rubricauloides*	Aphis holoenotherae
*Oe. sarmentosa*	[Cavariella aegopodii]
*Oe. serrulata* = Calylophus serrulata
*Oe. spectabilis*	Aphis oenotherae
*Oe. stricta*	Aphis oenotherae
*Oe. strigosa* var. subulifera	Myzus oenotherae
*Oe. stuchii*	[Aphis sp. nr holoenotherae – Rakauskas 2008]
*Oe. subterminalis* = Oenothera hazelae var. subterminalis
*Oe. subulifera* = Oenothera strigosa var. subulifera
*Oe. versicolor*	Brachycaudus helichrysi
*Oenothera* sp.	Aphis praeterita, sambuci; [Protaphis sp. (Utah, USA; A. Jensen, aphidtrek.org)

Key to apterae on Oenothera:-

1	ANT PT/BASE less than 0.5, with numerous long hairs. SIPH as large pores with surrounding hairs on shallow pigmented cones	…..Anoecia oenotherae
–	ANT PT/BASE more than 1.4, with few hairs. SIPH tubular	…..2
2	ANT tubercles undeveloped or weakly developed, so that front of head is convex, straight or sinuous in dorsal view	…..3
–	ANT tubercles well developed, so there is a deep frontal sinus in dorsal view	…..16
3	Cauda helmet-shaped, not longer than its basal width, with 4-8 hairs. SIPH have a distinct annular subapical incision. Spiracular apertures are large and rounded. ABD TERG 1 and 7 are without marginal tubercles (MTu)	…..4
–	Cauda tongue-shaped, as long as or longer than its basal width, with 4-21 hairs. SIPH without a subapical annular incision. Spiracular apertures reniform. ABD TERG 1 and 7 with MTu	…..5
4	Dorsal abdomen with an extensive solid black shield. ANT III 0.31-0.47 mm, 2.4-3.4 × HT II. R IV+V 0.17-0.24 mm. SIPH dark, imbricated, 1.7-3.4 × cauda	…..Brachycaudus cardui
–	Dorsal abdomen without a black shield. ANT III 0.07-0.25 mm, 0.9-2.2 × HT II. R IV+V 0.10-0.15 mm. SIPH pale, smooth, 0.8-2.0 × cauda	……Brachycaudus helichrysi
5	Cauda bluntly triangular, about as long as its basal width or only a little longer. ANT III with (0-)1-12 rhinaria on distal half	…..Protaphis middletonii
–	Cauda tongue-shaped, distinctly longer than its basal width. ANT III without rhinaria (except in alatiform specimens)	…..6
6	SIPH 2.2-4.5 × cauda, which is black and bears 9-20 hairs. ABD TERG 2-4(-6) as well as 1 and 7 with well-developed MTu	…..Aphis sambuci
–	SIPH 0.7-2.5 × cauda, if more than 2.1 × then cauda is pale or dusky and bears fewer hairs. ABD TERG 2-6 with or without small MTu	…..7
7	SIPH pale. R IV+V 0.13-0.18 mm long, with 5-12 accessory hairs. Cauda with 8-24 hairs	…..8
–	SIPH pale, dark, or dark-tipped. R IV+V 0.075-0.145 mm long, with 2 accessory hairs. Cauda with 4-24 hairs	…..11
8	ABD TERG 2-6 mostly with MTu, as well as ABD TERG 1 and 7	…..Aphis grossulariae
–	ABD TERG 2-6 without MTu	…..9
9	Tarsi almost completely smooth. Cauda with 16-24 hairs	…..Aphis epilobiaria
–	Tarsi distinctly imbricated. Cauda with 8-16 hairs	…..10
10	ANT PT/BASE 1.9-2.5 (usually more than 2)	…..Aphis oenotherae
–	ANT PT/BASE 1.5-2.3 (usually less than 2)	…..Aphis holoenotherae
11	ANT PT/BASE 3.3-4.7. Cauda with 5-8 hairs	…..Aphis praeterita
–	ANT PT/BASE 1.2-3.5 (if more than 3.1 then cauda has 11-24 hairs)	…..12
12	ANT PT/BASE 1.2-1.9. R IV+V 1.35-1.7 × HT II. Anterior half of subgenital plate with 4-6 hairs	…..Aphis oestlundi
–	ANT PT/BASE 1.9-3.5. R IV+V 0.9-1.4 × HT II. Anterior half of subgenital plate with 2-9 hairs	…..13
13	SIPH pale except at apices	.….Aphis nasturtii
–	SIPH dark	…..14
14	SIPH clearly darker than cauda, which bears 4-8 hairs. Longest hind femoral hairs only 0.4-0.7 × diameter of trochantro-femoral suture	……Aphis gossypii
–	Cauda always dark like SIPH, and bearing 7-24 hairs. Longest hind femoral hairs usually more than 0.7 × diameter of trochantro-femoral suture	…..15
15	Dorsal abdomen without any dark markings. Cauda usually with a midway constriction, and bearing 7-15 hairs	…..Aphis spiraecola
–	Dorsal abdomen with dark bands on ABD TERG 8, or 7 and 8, and often with dark markings anterior to SIPH. Cauda without any midway constriction, and bearing 11-24 hairs	…..Aphis fabae
16	SIPH with subapical reticulation (at least 4-5 rows of closed polygonal cells). Head smooth, with inner faces of ANT tubercles divergent	…..17
–	SIPH without subapical polygonal reticulation. Head spiculose, with inner faces of ANT tubercles parallel or apically convergent	…..18
17	SIPH variably pigmented, often dark distally. ANT VI BASE 0.65-0.95 × R IV+V. R IV+V 1.1-1.3 × HT II	…..Macrosiphum gaurae
–	SIPH usually pale, or only dusky at apices. ANT VI BASE 0.9-1.3 × R IV+V. R IV+V 0.85-1.1 × HT II	…..Macrosiphum euphorbiae
18	Longest hairs on ANT III more than 0.5 × BD III (?). ANT dark beyond basal half of ANT V. SIPH 1.4-1.9 × cauda (?)	…..Myzus biennis (or oenotherae? – see text)*
–	Longest hairs on ANT III less than 0.5 × BD III. ANT pale except for segmental apices. SIPH 1.9-2.5 × cauda	…..19
19	ANT III with (0-) 1-2 (-3) small rhinaria near base. Inner faces of ANT tubercles approximately parallel-sided. SIPH tapering/cylindrical on distal half	…..Aulacorthum solani
–	ANT III without rhinaria. Inner faces of ANT tubercles apically convergent. SIPH slightly swollen on distal half	…..Myzus persicae

*Ohwia*	Fabaceae
*Ohwia caudata*	Aphis gossypii

*Oldenlandia*	Rubiaceae
*Oldenlandia corymbosa*	Aphis gossypii; Myzus persicae
*O. herbacea*	Aphis gossypii
*O. sclerophylla*	Aphis gossypii
*Oldenlandia* spp.	[Acyrthosiphon pisum]; Aulacorthum solani; [Lipaphis pseudobrassicae]; Myzus cymbalariae; Uroleucon compositae

Use key to polyphagous aphids.

*Oldfeltia*	Asteraceae
*Oldfeltia polyphlebia* see Senecio polyphlebius

*Olea* Olives	Oleaceae
*Olea europaea*	Prociphilus oleae; [Tetraneura agnesii del Guercio 1920]

*Olearia*	Asteraceae
*Olearia bullata*	[Aphis sp. near coprosmae (New Zealand; Teulon et al. 2013)]
*O. gunniana*	Aphis gossypii; [Uroleucon sp. (Leonard 1972a)]
*O. lirata*	[Uroleucon sp. (Leonard 1972a)]
*O. passerinoides*	Myzus persicae; [Uroleucon sp. (Leonard 1972a)]
*O. pimeleoides*	[Uroleucon sp. (Leonard 1972a)]
O. viscidula	Myzus persicae; [Uroleucon sp. (Leonard 1972a)]

Use key to polyphagous aphids. (Note: the Uroleucon is a large, red, apparently undescribed species.)

*Oligostachyum*	Poaceae
*Oligostachyum shiuyingianum*	Ceratovacuna hoffmanni; Chaitoregma tattakana

Use key to aphids on Arundinaria.

*Oligotrichum*	Polytrichaceae
*Oligotrichum aligerum*	Myzodium modestum

Use key to apterae of moss-feeding aphids under Polytrichum.

*Omalotheca*	Asteraceae
*Omalotheca caucasica* = Gnaphalium sylvaticum

*Oncidium*	Orchidaceae
*Oncidium altissimum*	Cerataphis orchidearum; Myzus persicae; Sitobion luteum
*O. cebolleta* = Trichocentrum cebolleta
*O. sphacelatum*	Aphis (Toxoptera) aurantii

Use key to apterae on orchids under Cymbidium.

*Oncoba*	Salicaceae
*Oncoba spinosa*	Aphis (Toxoptera) aurantii; Schoutedenia ralumensis

Key to apterae on Oncoba:-

–	ABD TERG 7 with a pair of long, pointed backwardly-directed processes. SIPH as short broad cones. ANT 5-segmented. ANT PT/BASE less than 1	.… Schoutedenia ralumensis
–	ABD TERG 7 without long processes. SIPH tubular, dark, much longer than wide. ANT 6-segmented, with ANT PT/BASE 3.5-5.0	….. Aphis (Toxoptera) aurantii

*Oncosiphon*	Asteraceae
*Oncosiphon piluliferum*	Aphis craccivora

*Onobrychis*	Fabaceae
*Onobrychis arenaria* ssp. sibirica	Aphis craccivora
*O. argentea* ssp. hispanica = O. conferta ssp. hispanica
*O. conferta* ssp. hispanica	Aphis craccivora
*O. cyri*	Aphis craccivora
*O. gracilis*	Acyrthosiphon pisum
*O. kachetica*	Acyrthosiphon pisum; Aphis craccivora, fabae; Therioaphis trifolii
*O. micrantha*	Aphis craccivora
*O. montana*	Acyrthosiphon pisum; Aphis craccivora
*O. pulchella*	Aphis craccivora, [“laburni” (= cytisorum?)]
*O. sativa* = O. viciifolia
*O. sibirica* = O. arenaria ssp. sibirica
*O. squarrosa*	Acyrthosiphon pisum
*O. tanaitica* (= O. arenaria)	Aphis craccivora
*O. transcaucasica*	Aphis craccivora
*O. viciifolia*	Acyrthosiphon loti, pisum; Aphis [craccae], craccivora, fabae, pseudocomosa; [Brachycaudus persicae]; Therioaphis trifolii
*Onobrychis* sp.	[Smynthurodes betae]

Key to apterae on Onobrychis:-

1	Fore coxae greatly enlarged. SIPH in form of truncate cones. Cauda knobbed, anal plate bilobed. Dorsal hairs with expanded apices, and arising from pigmented, tuberculate bases	.….Therioaphis trifolii
–	Fore coxae normal. SIPH tubular. Cauda tongue- or finger-shaped, anal plate entire. Dorsal hairs with blunt or pointed apices, not arising from tuberculate bases	..…2
2	Body pale, spindle-shaped; BL 2.0-4.4 mm. ANT tubercles well developed with inner faces divergent. SIPH and cauda pale	…..3
–	Body oval, with an extensive dark dorsal shield; BL 1.4-2.2 mm. ANT tubercles weakly developed. SIPH and cauda both dark	…..4
3	ANT I longer than wide and bearing 9-23 hairs. SIPH attenuate distally, thinner than hind tibia at midlength	…..Acyrthosiphon pisum
–	ANT I not longer than wide, bearing 6-10 hairs. SIPH not attenuate distally, as thick as or thicker than hind tibia at midlength	…..Acyrthosiphon loti
4	Longest ANT hairs 0.67-1.4 × ANT BD III. Femoral hairs about as long as trochantro-femoral suture. Cauda with 8-19 hairs (rarely less than 10)	…..Aphis pseudocomosa
–	Longest ANT hairs 0.37-0.75 × ANT BD III. Femoral hairs shorter. Cauda with 4-9 hairs	…..Aphis craccivora

*Onoclea*	Woodsiaceae
*Onoclea sensibilis*	Amphorophora ampullata, ampullata ssp. laingi; Aulacorthum solani; Neomyzus circumflexus
*O. struthiopteris* see Matteuccia

Use key to fern-feeding aphids under Polypodium.

*Ononis*	Fabaceae
*Ononis alba*	Therioaphis obscura
*O. antiquorum* = O. spinosa ssp. antiquorum
*O. aragonensis*	Aphis fabae
*O. arvensis* = O. spinosa ssp. hircina
*O. austriaca* = O. spinosa ssp. austriaca
*O. diffusa*	Therioaphis ononidis
*O. fruticosa*	Acyrthosiphon loti, ononis; Aphis brunnea
*O. hircina* = O. spinosa ssp. hircina
*O. leiosperma* = O. spinosa ssp. leiosperma
*O. minutissima*	Aphis craccivora; Therioaphis alatina
*O. natrix* (incl. sspp. angustissima, ramosissima)	Acyrthosiphon pilosum, pisum; Aphis brunnea, craccivora, [medicaginis]; [Myzus persicae]; Therioaphis alatina, natricis, trifolii
*O. pseudohircina* = spinosa ssp. hircina
*O. pubescens*	Aphis brunnea
*O. pusilla*	Therioaphis alatina
*O. ramosissima* = natrix ssp. ramosissima
*O. reclinata*	Therioaphis obscura
*O. repens* (= O. spinosa ssp. procurrens)	Acythrosiphon loti, ononis, pisum; Aphis kaltenbachi; Macrosiphum euphorbiae; Therioaphis ononidis, trifolii
*O. repens* var. mitis = O. spinosa ssp. hircina
*O. serrata*	Therioaphis ononidis
*O. spinosa* (incl. ssp. antiquorum, austriaca, hircina)	Acyrthosiphon ononis, pilosum, pisum; Aphis brunnea, craccivora, cytisorum, kaltenbachi, ?medicaginis; Brachycaudus helichrysi; Macrosiphum euphorbiae; [Myzus sp. (Bozhko 1976a)]; Therioaphis alatina, hungarica, natricis, obscura, ononidis, trifolii
*O. stenophylla*	Therioaphis natricis
*O. tridentata*	Aphis cytisorum, kaltenbachi, ononidis
*O. viscosa*	Aphis brunnea; Therioaphis alatina

Key to apterae on Ononis:-

(Couplets 1-3 can be applied to alatae as well as apterae.)

1	Fore coxae greatly enlarged. SIPH in form of truncate cones. Cauda knobbed, anal plate bilobed. Dorsal hairs with expanded apices, and arising from tuberculate bases that are often pigmented	.….2
–	Fore coxae normal. SIPH tubular. Cauda tongue- or finger-shaped, anal plate entire. Dorsal hairs with blunt or pointed apices, not arising from tuberculate bases	..…7
2	ABD TERG 1-4 each bearing 7-10 (mostly 8) long hairs	…..Therioaphis trifolii
–	ABD TERG 1-4 each with 4 long hairs (one spinal pair and one marginal pair; occasionally there are also one or two much smaller hairs)	…..3
3	R IV+V distinctly longer than HT II, and bearing 8-27 accessory hairs	…..4
–	R IV+V 0.7-0.95 × HT II, and bearing 2-8 (-9) accessory hairs	…..6
4	All adult viviparae alate. ABD TERG 8 with 2 (-3) hairs. (R IV+V with 17-25 accessory hairs)	…..Therioaphis alatina
–	Predominant morph apterous. ABD TERG 8 with 4-6 hairs	…..5
5	R IV+V with 14-27 accessory hairs	…..Therioaphis natricis
–	R IV+V with 8-12 accessory hairs	…..Therioaphis ononidis
6	ABD TERG 1-7 with very large paired variably pigmented sclerotic cross-bars, often fused across midline. R IV+V with 2-4 accessory hairs	…..Therioaphis obscura
–	ABD TERG 1-7 with hairs arising from separate sclerotic plates that are rarely fused across midline. R IV+V with 6-9 accessory hairs	…..Therioaphis hungarica
7	Body spindle-shaped. ANT tubercles well developed, with inner faces smooth and divergent. ANT often longer than BL	…..8
–	Body oval. ANT tubercles undeveloped or weakly developed, ANT shorter than BL	…..12
8	SIPH with subapical polygonal reticulation. Longest hairs on ANT III more than 0.5 × basal diameter of segment	…..Macrosiphum euphorbiae
–	SIPH without subapical polygonal reticulation. Longest hairs on ANT III usually less than 0.5 × basal diameter of segment	…..9
9	R IV+V with 19-36 accessory hairs. First tarsal segments usually with 5 hairs. Prominent marginal tubercles present on several of ABD TERG 2-4(-5)	…..Acyrthosiphon pilosum
–	R IV+V with 3-12 accessory hairs. First tarsal segments with 3 hairs. Abdominal marginal tubercles either absent or small and inconspicuous	…..10
10	ANT I with 6-9 hairs. ANT BASE VI 1-1.5 × longer than R IV+V. SIPH not attenuate distally; diameter at midlength greater than middle diameter of hind tibia	..…Acyrthosiphon loti
–	ANT I with 9-23 hairs. ANT BASE VI 1.6-2.9 × longer than R IV+V. SIPH attenuate distally, with diameter at midlength similar to or less than middle diameter of hind tibia	..…11
11	ANT VI BASE 1.6-1.9 × R IV+V, which bears (6-) 8-12 accessory hairs. R IV+V 0.75-0.95 × HT II. Cauda with 11-23 hairs	…..Acyrthosiphon ononis
–	ANT VI BASE 1.9-2.9 × R IV+V which bears 3-7 (-8) accessory hairs. R IV+V 0.67-0.85 × HT II. Cauda with 8-14 hairs	…..Acyrthosiphon pisum
12	Cauda helmet-shaped, not longer than its basal width. SIPH pale, smooth, with a subapical annular incision. Spiracular apertures large and rounded. ABD TERG 1 and 7 without marginal tubercles (MTu). Dorsal abdomen without dark markings	…..Brachycaudus helichrysi
–	Cauda tongue- or finger-shaped, longer than its basal width. SIPH dark, imbricated, without a subapical annular incision. Spiracular apertures reniform. ABD TERG 1 and 7 always with MTu. Dorsal abdomen usually with dark markings	…..13
13	SIPH very short, flangeless, 0.2-0.3 × cauda. Dorsum usually with a solid dark shield from metanotum to ABD TERG VI	…..Aphis kaltenbachi
–	SIPH with a distinct flange, and at least 0.8 × cauda. Dorsum with or without a solid dark shield	…..14
14	Very short haired; hairs on ABD TERG 8 are 11-16 μm, and on ABD TERG 3 marginally 11-12 μm. Posterior hair on hind trochanter 16-24 μm, 0.29-0.52 × length of trochantro-femoral suture	…..Aphis ?medicaginis (see text)
–	Longer haired; hairs on ABD TERG 8 are 18-85 μm, and on ABD TERG 3 marginally 12-85 μm. Posterior hair on hind trochanter (0.34-) 0.5-2.0 × length of trochantro-femoral suture	…..15
15	ABD TERG 1-4 and 7, and sometimes also 5 and 6, with MTu. R IV+V 1.1-1.45 × HT II and bearing 2-6 (usually 4-5) accessory hairs	…..Aphis brunnea
–	MTu only sporadically present on ABD TERG 2-4. R IV+V 0.9-1.2 × HT II, with 2 accessory hairs	…..16
16	Cauda with 11-25 hairs. Dorsal abdomen usually with a few small dark spots anterior to SIPH	…..Aphis fabae
–	Cauda with 4-13 hairs. Dorsal abdomen usually with extensive dark sclerotisation	…..17
17	R IV+V 0.88-1.16 × HT II (mostly 0.9-1.05 ×). Anterior half of genital plate with 2 (-3) hairs	…..Aphis craccivora
–	R IV+V 0.97-1.3 × HT II (mostly 1.06-1.2 ×). Anterior half of genital plate with 2-8 hairs (mode 4, mean 5.2)	…..Aphis cytisorum

*Onopordum*	Asteraceae
*Onopordum acanthium*	Aphis craccivora, fabae, gossypii, solanella, [symphyti]; Brachycaudus cardui, cardui ssp. turanica, helichrysi; Capitophorus carduinus, elaeagni; Dysaphis lappae ssp. cynarae; Macrosiphum euphorbiae; Myzus persicae; Protaphis anuraphoides, [elongata], pseudocardui, terricola; Trama troglodytes; Uroleucon aeneum, bicolor (?), [sonchi]
*O. anisacanthum* = O. heteracanthum
*O. davisii*	Aphis craccivora, spiraecola; Brachycaudus cardui
*O. heteracanthum*	Aphis fabae; Myzus persicae
*O. illyricum*	Aphis fabae; Brachycaudus cardui, helichrysi; Uroleucon aeneum, [sonchi]
*O. leptolepis*	Brachycaudus cardui; Protaphis [carthami], terricola
*O. nervosum*	Brachycaudus cardui
*O. olgae*	Pemphigus bursarius; Rectinasus buxtoni; Smynthurodes betae
*O. sibthorpianum*	Protaphis terricola
*O. tauricum*	Brachycaudus cardui

Key to apterae on Onopordum:-

1	SIPH absent. ANT PT/BASE less than 0.5. Eyes reduced, often to triommatidia	…..2
–	SIPH present. ANT PT/BASE more than 0.6. Eyes well-developed	…..5
2	Body and antennae sparsely hairy. Wax glands present on ABD TERG 3-7	…..Pemphigus bursarius
–	Body and antennae densely hairy, e.g. base of last antennal segment with more than 20 hairs. Wax glands absent or inconspicuous	…..3
3	HT II elongate, at least 0.5 × hind tibia. ANT 6-segmented	…..Trama troglodytes
–	HT II of normal length. ANT 5-segmented	…..4
4	ANT V BASE and R IV+V both very long, respectively about 1.7 and 2.5 × width of head between antennal bases. ANT II similar in length to ANT I, much shorter than III	.….Rectinasus buxtoni
–	ANT V BASE and R IV+V of normal length , both about 0.5 × width of head between antennal bases. ANT II about twice as long as ANT I, similar in length to III	..…Smynthurodes betae
5	Cauda short, helmet-shaped or bluntly triangular, shorter than or not clearly longer than its basal width in dorsal view	…..6
–	Cauda elongate triangular, tongue-or finger-shaped, clearly longer than its basal width in dorsal view	…..11
6	ANT PT/BASE 0.75-1.15. Cauda bluntly triangular with 10-24 hairs. ABD TERG 1 and 7 with well-developed marginal tubercles (MTu)	…..7
–	ANT PT/BASE 2.3-5.1. Cauda helmet-shaped, with 5-8 hairs. If ABD TERG 1 and 7 have MTu then these are also present on ABD TERG 2-5	…..9
7	ANT III usually without secondary rhinaria (rarely with 1-3). (Longest hairs on ABD TERG 3 are 0.7-1.1 × ANT BD III)	…..Protaphis pseudocardui
–	ANT III and IV usually with rhinaria (0-12 on III and 0-4 on IV)	…..8
8	Longest hairs on ABD TERG 3 are 1.2-1.3 × ANT BD III. SIPH 0.9-1.2 × cauda, and with a distinct flange. R IV+V 1.45-1.65 × HT II	…..Protaphis anuraphoides
–	Longest hairs on ABD TERG 3 are 0.3-0.9 × ANT BD III. SIPH 0.67-0.92 × cauda, with a weak flange . R IV+V 1.2-1.4 (-1.5) × HT II	……Protaphis terricola
9	Dorsal abdomen with an extensive solid black patch. SIPH 0.10-0.15 × BL. Mesosternum with a pair of dark mammariform processes	…..Brachycaudus cardui
–	Dorsal abdomen without a solid black patch, at most with scattered dark markings. SIPH 0.05-0.10 × BL. Mesosternum without mammariform processes	…..10
10	BL 0.9-2.0 mm. SIPH smooth, short and broad-based, 1.5-2.0 × their diameter at midlength. Spinal and marginal tubercles (STu and MTu) rare or absent	……Brachycaudus helichrysi
–	BL 2.1-3.0 mm. SIPH imbricated and about 3 × their diameter at midlength. Numerous well-developed STu and MTu present	…..Dysaphis lappae ssp. cynarae
11	Hairs on front of head and dorsal body mostly long and capitate, and arising from tuberculate bases	…..12
–	Hairs on front of head and dorsal body not capitate	…..13
12	Cauda 1.1-1.5 × R IV+V, and bearing 5-8 hairs. ANT PT 3.1-4.4 × R IV+V, and ANT PT/BASE 4.6-6.3. SIPH without dark apices	…..Capitophorus carduinus
–	Cauda 1.4-2.3 × R IV+V, and bearing 7-13 hairs. ANT PT 4.5-6.3 × R IV+V, and ANT PT/BASE 6.0-9.2. SIPH with dark apices	…..Capitophorus elaeagni
13	BL 3.5-5.0 mm. ANT III with 17-45 rhinaria. SIPH dark, with reticulation extending over distal 0.15-0.25 of length	…..14
–	BL less than 3.5, and other characters not in that combination	…..go to key to polyphagous aphids
14	Cauda black. ABD TERG 2-4 consistently with well-developed MTu. R IV+V 1.2-1.3 × HT II	…..Uroleucon aeneum
–	Cauda pale. ABD TERG 2-3 irregularly with very small MTu. R IV+V 0.79-0.84 × HT II	…..Uroleucon bicolor (? – see text)

*Onosma*	Boraginaceae
*Onosma stellulata*	Brachycaudus cardui

*Onosmodium*	Boraginaceae
Onosmodium bejariense var. occidentale	Brachycaudus helichrysi

*Onychium*	Adiantaceae
*Onychium japonicum*	Idiopterus nephrelepidis

*Ophiopogon*	Asparagaceae
*Ophiopogon japonicus*	Hydronaphis sp. (Japan – Moritsu 1983)

*Ophiorrhiza*	Rubiaceae
*Ophiorrhiza* sp.	Aphis spiraecola

*Ophiuros*	Poaceae
*Ophiuros exaltatus*	[Iowana zhangi]; Rhopalosiphum maidis

*Ophrys*	Orchidaceae
*Ophrys apifera*	Aphis fabae
*O. fusca*	Dysaphis neostroyani
*O. sphegodes* (incl. arenifera)	Aphis fabae
*O. × todaroana*	Aphis fabae

Use key to apterae of orchid-feeding aphids under Cymbidium.

*Oplismenus*	Poaceae
*Oplismenus burmannii*	Hysteroneura setariae; Tetraneura akinire
*O. compositus*	Asiphonella dactyloni; [Ceratovacuna nekoashi]; [Hyalomyzus raoi]; Hysteroneura setariae; Micromyzodium spinulosum; Pentalonia gavarri; Pseudoregma panicola; Sitobion miscanthi
*O. hirtellus*	Pseudoregma panicola
*O. imbecillis* = O. hirtellus
*O. setarius* = O. compositus
*O. undulatifolius*	[Ceratovacuna nekoashi]; Pseudoregma panicola; Sitobion akebiae
*Oplismenus* spp.	Baizongia pistaciae; Ceratovacuna lanigera; [Pseudoregma koshunensis]

Use key to apterae of grass-feeding aphids under Digitaria.

*Oplopanax*	Araliaceae
*Oplopanax horridum*	Aphis asclepiadis; Macrosiphum sp. nr euphorbiae (see aphidtrek.org)
Use key to polyphagous aphids.

*Opopanax*	Apiaceae
*Opopanax chironius*	Anuraphis pyrilaseri, shaposhnikovi; Aphis fabae; Dysaphis apiifolia

Key to apterae on Opopanax:-

(All 4 species have undeveloped or weakly-developed ANT tubercles, dark SIPH, dark cross-bands on ABD TERG 8 or 7-8, and usually some scattered dark markings on ABD TERG 1-6.)

1	Cauda distinctly longer than its basal width. Spinal tubercles (STu) absent, abdominal marginal tubercles (MTu) consistently present only on ABD TERG 1 and 7	…..Aphis fabae
–	Cauda helmet-shaped, a little shorter than its basal width. STu present on head and at least some ABD TERG, and MTu on ABD TERG 1-5 or 1-7	…..2
2	R IV+V much shorter than SIPH. SIPH more than 3 × basal width with normal imbrication. Cauda with 5 hairs	…..Dysaphis apiifolia
–	R IV+V longer than SIPH. SIPH less than 2.5 × basal width with close-set rows of spinules. Cauda with 11-18 hairs	…..3
3	MTu on ABD TERG 1-5 only. R IV+V 1.6-2.1 × HT II	…..Anuraphis pyrilaseri
–	MTu on ABD TERG 1-7. R IV+V 1.2-1.6 × HT II	…..Anuraphis shaposhnikovi

*Opulaster*	Rosaceae
*Opulaster malvaceus*	Utamphorophora humboldti
*O. opulifolius*	Aphis neilliae, [pomi], spiraecola; [Chaetosiphon tetrarhodum]; Rhopalosiphum padi; Utamphorophora humboldti; [aphid gall – Wahlgren 1956, 51]

See key to apterae under Physocarpus.

*Opuntia*	Cactaceae
*Opuntia aurantiaca*	Protaphis middletonii
*O. dillenii*	Aphis gossypii
*O. ficus-indica*	Aphis craccivora, fabae; Myzus persicae; Protaphis middletonii
*O. inermis* = O. stricta
*O. stricta*	Pentalonia nigronervosa; Protaphis middletonii
*O. vulgaris* = O. ficus-indica
*Opuntia* sp.	Aphis gossypii

Key to apterae on Opuntia:-

–	ANT longer than BL, with ANT PT/BASE 5-8. Femora with basal 0.6 or more of length pale, rest contrastingly black. SIPH pale basally and dark distally. (Al. with broad-banded wing-veins, and radius fused with media to form a closed cell below pterostigma)	….. Pentalonia nigronervosa
–	Without that combination of characters	…..go to key to polyphagous aphids

*Orchis*	Orchidaceae
*Orchis anthropophora*	Aphis fabae
*O. coriophora* = Anacamptis coriophora
*O. purpurea*	Aphis orchidis
*Orchis* spp.	Aulacorthum solani; Dysaphis neostroyani; Myzus persicae; Neomyzus circumflexus

Use key to apterae of orchid-feeding aphids under Cymbidium.

*Oreocnide* (including Villebrunea)	Urticaceae
*Oreocnide frutescens*	Aulacorthum solani
*O. integrifolia*	[Greenidea bucktonis]

*Oreopanax*	Araliaceae
*Oreopanax guatemalensis*	Myzus persicae

*Origanum* (including Majorana)	Lamiaceae
*Origanum compactum*	Aphis sp. near gossypii
*O. creticum* = O. vulgare
*O. heracleoticum* = O. vulgare ssp. viridulum
*O. majorana* (= Majorana hortensis)	Myzus ornatus; Neomyzus circumflexus
*O. × paniculatum*	Aphis origani
*O. syriacum*	Eucarazzia elegans
*O. tyttanthum* = O. vulgare ssp. gracile
*O. virens* = O. vulgare ssp. virens
*O. vulgare* (incl. sspp. gracile, virens, viridulum)	Aphis fabae, gossypii, nasturtii, origani; Aulacorthum solani; Kaltenbachiella pallida; Myzus ornatus, persicae; [Ovatomyzus chamaedrys]; Ovatus crataegarius

Key to apterae on Origanum:-

1	ANT usually 4-segmented, 0.12-0.15 × BL, with PT/BASE less than 0.5. Eyes 3-facetted. SIPH absent. Legs very short, with fore- and mid-tarsi usually 1-segmented. Dorsal wax glands present on head, thorax and ABD TERG 1-8, comprising facets surrounding an elongate central area	…..Kaltenbachiella pallida
–	ANT 5- or 6-segmented, more than 0.5 × BL, with PT/BASE more than 1. Eyes multifacetted, SIPH present, tarsi 2-segmented and wax glands not evident	…..2
2	SIPH strongly swollen, 5.4-8.2 × cauda, with maximum diameter of swollen part more than 2 × minimum diameter of stem, smooth except for a little subapical polygonal reticulation	…..Eucarazzia elegans
–	SIPH not swollen or much less swollen, and less than 3.5 × cauda	…..3
3	Head smooth, ANT tubercles weakly developed. Marginal tubercles (MTu) present on ABD TERG 1 and 7	…..4
–	Head spiculose with well-developed ANT tubercles, their inner faces spiculose or scabrous and steep-sided. MTu absent from ABD TERG 1 and 7	…..7
4	SIPH pale with dark apices	…..Aphis nasturtii
–	SIPH wholly dark	…..5
5	Cauda with 11-24 hairs. Hairs on ANT III 0.8-3.4 × BD III	…..Aphis fabae
–	Cauda with 4-8 hairs. Hairs on ANT III 0.3-0.7 × BD III	…..6
6	SIPH 0.10-0.12 × BL, 1.05-1.45 × cauda. ABD TERG 7 and 8 usually with dark cross-bands	…..Aphis origani
–	SIPH 0.12-0.26 × BL, 1.3-2.5 × cauda. ABD TERG 7 and 8 rarely with dark cross-bands	…..Aphis gossypii
7	Dorsal abdomen without any dark markings	…..8
–	Dorsal abdomen with dark markings	…..10
8	SIPH slightly but distinctly swollen on distal half. ANT 0.7-1.0 × BL	…..Myzus persicae
–	SIPH tapering/cylindrical on distal half. ANT 1.1-1.5 × BL	…..9
9	Inner faces of ANT tubercles with convergent, rounded, scabrous processes. ANT III without rhinaria. ANT PT/BASE 5.2-7.6. R IV+V 1.3-1.6 × HT II, with 2-4 accessory hairs	…..Ovatus crataegarius
–	Inner faces of ANT tubercles without processes, approximately parallel. ANT III usually with 1-2 small rhinaria near base. ANT PT/BASE 4.0-5.4. R IV+V 1.1-1.4 × HT II, with 5-7 accessory hairs	…..Aulacorthum solani
10	Dorsal abdomen with a large, roughly U-shaped black patch. ANT PT/BASE 4.3-5.2	…..Neomyzus circumflexus
–	Dorsal abdomen with a pattern of dark intersegmental markings. ANT PT/BASE 1.7-2.8	…..Myzus ornatus

*Orixa*	Rutaceae
*Orixa japonica*	?Aulacorthum ?solani (as Myzus kusaki Shinji); Pseudomegoura magnoliae

Use key to polyphagous aphids.

*Orlaya*	Apiaceae
*Orlaya grandiflora*	Aphis solanella; Cavariella theobaldi; Dysaphis crataegi; Hyadaphis passerinii

Key to apterae on Orlaya:-

1	SIPH dark, clavate and about equal in length to the dark cauda	…..Hyadaphis passerinii
–	SIPH pale or dark, tapering/cylindrical, longer than cauda, which may also be pale or dark	…..2
2	ABD TERG 8 with a backwardly-pointed process bearing 2 hairs	…..Cavariella theobaldi
–	No process on ABD TERG 8	…..3
3	Cauda helmet-shaped, not longer than its basal width, usually with 5 hairs. Spinal tubercles (STu) present on head and ABD TERG 8 or, 7 and 8, and marginal tubercles (MTu) on ABD TERG 1-5, but not usually on 7	…..Dysaphis crataegi
–	Cauda tongue-shaped, longer than its basal width, with 11-23 hairs. STu absent, and MTu only regularly present on ABD TERG 1 and 7	…..Aphis fabae group (incl. solanella)

Ormenis see Chamaemelum

Asteraceae

*Ornithidium*	Orchidaceae
*Ornithidium adendrobium*	Cerataphis orchidearum

*Ornithogalum*	Asparagaceae
*Ornithogalum dubium*	Aphis gossypii
*Ornithogalum* spp.	Myzus persicae; Rhopalosiphum nymphaeae, padi

Key to apterae on Ornithogalum:-

–	Dorsal cuticle with a pattern of spinules arranged in polygons, with 1-3 spicules in the centre of each polygon. SIPH clavate	….. Rhopalosiphum nymphaeae
–	Without the above combination of characters; if dorsal cuticle has a pattern of spinules arranged in polygons then SIPH not clavate	…..go to key to polyphagous aphids

*Ornithopus*	Fabaceae
*Ornithopus compressus*	Aphis craccivora
*O. isthmocarpus* = O. sativus ssp. isthmocarpus
*O. perpusillus*	Acyrthosiphon pisum; Aphis craccivora
*O. sativus* (incl. ssp. isthmocarpus)	Aphis craccivora

Key to apterae on Ornithopus:-

–	Body oval, with an extensive black sclerotic dorsal shield, BL 1.4-2.2 mm. SIPH and cauda black	….. Aphis craccivora
–	Body spindle-shaped, pale, BL 2.5-4.4 mm. SIPH and cauda pale. (Additional check – ANT VI BASE 0.25-0.4 mm, 1.8-2.3 × R IV+V – otherwise go to key to polyphagous aphids)	….. Acyrthosiphon pisum

*Orobanche* (including Aphyllon)	Orobanchaceae
*Orobanche aegyptiaca*	Aphis gossypii, [Aphis sp. (Davletshina 1964)]; Rectinasus buxtoni; Smynthurodes betae
*O. foetida*	[Geoica utricularia]
*O. crenata*	Smynthurodes betae
*O. hederae*	Macrosiphum euphorbiae
*O. lutea*	[Aphis orobanches]
*O. mutelii*	[Aphis orobanches]
*O. ramosa*	[Aphis orobanches]; [Dysaphis candicans]; [Brachycaudus cardui (? – as Aphis phelipaeae Passerini)]; Smynthurodes betae
*O. variegata*	Smynthurodes betae
*Orobanche* sp.	[Anuraphis subterranea]; Protaphis middletonii; [Siphonophora orobanches Lichtenstein (nomen nudum)]; Myzus persicae; Rhopalosiphum rufiabdominale; Trama orobanches

Key to apterae on Orobanche:-

[Only the original descriptions of Aphis orobanches and Dysaphis candicans are available (Passerini 1879), and are insufficient to include these species in the key; see text under these names for further information.]

1	ANT 5-segmented, with ANT V BASE very long, more than 15 × longer than the short peg-like PT. R IV+V extremely long, similar in length to hind femur	…..Rectinasus buxtoni
–	ANT 5- or 6-segmented, base of last segment and R IV+V relatively much shorter	…..2
2	HT II greatly elongated, more than 0.5 × hind tibia	…..Trama orobanches
–	HT II of normal length	…..3
3	Thoracic spiracles greatly enlarged, rounded, much larger than abdominal spiracles. ANT PT/BASE 7.0-11.4, usually more than 8.0. ANT III with 14-36 rhinaria	…..Nasonovia ribisnigri
–	Thoracic spiracles similar in size to abdominal ones. ANT PT/BASE less than 6. ANT III with 0-10 rhinaria	…..go to key to polyphagous aphids

*Orostachys*	Crassulaceae
*Orostachys spinosa*	Aphis sedi

Ortantha see Odontites

Orobanchaceae

*Orthilia* (including Ramischia)	Ericaceae
*Orthilia secunda*	Aulacorthum pirolacearum

*Orthocarpus*	Orobanchaceae
*Orthocarpus luteus*	Nasonovia alpina
*O. purpurascens* (= Castelleja exserta)	Macrosiphum orthocarpus

Key to apterae on Orthocarpus:-

–	BL 1.9-2.5 mm. ANT III-V dark only at apices, and SIPH pale or uniformly pigmented, without subapical polygonal reticulation. (Also check: thoracic spiracular apertures much larger than abdominal ones, which are almost covered by cowl-like opercula. R IV+V 1.6-2.1 × HT II with 12-18 accessory hairs)	….. Nasonovia alpina
–	BL more than 3 mm. ANT black beyond basal part of III. SIPH black on distal c.0.7 (and with subapical reticulation?)	…..Macrosiphum orthocarpus*

Orthostemon = Acca

Myrtaceae

Oryza

Poaceae

Oryza sativa

Anoecia corni, fulviabdominalis; Aphis gossypii; Brachysiphoniella montana; Chaetogeoica polychaeta; Diuraphis noxia; Forda orientalis; Geoica lucifuga, setulosa, utricularia; Hyalopterus amygdali; Hysteroneura setariae; Melanaphis sacchari; Metopolophium dirhodum; Paracletus cimiciformis; [Prociphilus sp.]; Rhopalosiphum maidis, nymphaeae, padi, rufiabdominale, rufulum; Schizaphis graminum; Sipha flava, glyceriae, maydis; Sitobion akebiae, avenae, graminis, miscanthi; Tetraneura akinire, basui, javensis, nigriabdominalis, radicicola, ulmi

Use key to apterae of grass-feeding aphids under Digitaria, or for a simple key to common aphids on rice see Blackman & Eastop 2000.

*Oryzopsis* (including Eriocoma, Piptantherum)	Poaceae
*Oryzopsis cuspidata* = O. hymenoides
*O. hymenoides*	Forda marginata
*O. lateralis*	Sitobion himalayensis
*O. miliacea*	Melanaphis sacchari; Myzus persicae; Sitobion avenae

Use key to apterae of grass-feeding aphids under Digitaria.

*Osbeckia*	Melastomataceae
*Osbeckia capitata*	Aphis gossypii, nasturtii; [Capitophorus carduinus]; Myzus ornatus, persicae
*O. chinensis*	Aphis nasturtii; Brachycaudus helichrysi; [Rhopalosiphum rufiabdominale]
*O. crinata*	Aphis aurantii, gossypii; [Capitophorus sp.]; Myzus persicae

Use key to polyphagous aphids.

*Osmanthus*	Oleaceae
*Osmanthus aquifolius*	Prociphilus osmanthae
*O. asiaticus*	[Shivaphis hangzhouensis]
*O. aurantiacus*	Prociphilus osmanthae
*O. aurantiacus* var. thunbergii	Pseudomegoura magnoliae
*O. × burkwoodii*	Prociphilus osmanthae
*O. heterophyllus*	Prociphilus osmanthae
*O. insularis*	Aphis odinae

Key to apterae on Osmanthus:-

–	SIPH absent. ANT PT/BASE less than 1	….. Prociphilus osmanthae
–	SIPH present. ANT PT/BASE more than 1	…..go to key to polyphagous aphids

Osmaronia see Oemleria

Rosaceae

Osmia see Eupatorium

Asteraceae

*Osmorhiza*	Apiaceae
*Osmorhiza aristata* (incl. var. longistylis)	Aphis fabae; Cavariella aegopodii, theobaldi; Semiaphis heraclei; [Uroleucon parvotuberculatum]
*O. chilensis*	Macrosiphum euphorbiae; Myzus ascalonicus; [Rhopalosiphoninus staphyleae]
*O. claytoni* = O. aristata
*O. longistylis* see aristata
*Osmorhiza* sp.	Aphis asclepiadis

Use key to apterae on Apium.

*Osmunda*	Osmundaceae
*O. cinnamomea*	Amphorophora ampullata ssp. laingi
*O. japonica*	Amphorophora ampullata; Aulacorthum solani; Taiwanomyzus babai, filicis
*O. regalis*	Aulacorthum solani; Macrosiphum walkeri; Micromyzella pterisoides; Neomyzus circumflexus
*Osmunda* sp.	Macrosiphum euphorbiae

Use key to apterae on ferns under Polypodium.

*Osmundastrum*	Osmundaceae
*Osmundastrum asiaticum*	Micromyzus nikkoensis, osmundae
*O. claytonianum*	Micromyzus osmundae

Use key to apterae on ferns under Polypodium.

*Osteomeles*	Rosaceae
*Osteomeles schwerinae*	Myzus persicae
*O. subrotunda*	Aphis gossypii

Use key to polyphagous aphids.

*Osteospermum*	Asteraceae
*Osteospermum ecklonis*	Macrosiphum euphorbiae; Uroleucon compositae
*O. moniliferum* = Chrysanthemoides monilifera
*O. spinescens*	Aphis craccivora
*O. vaillantii* = Tripteris vaillantii

Use key to polyphagous aphids.

*Ostericum*	Apiaceae
*Ostericum melanotilingia* = Angelica decursiva

*Ostrya* Hop-hornbeams	Corylaceae
*Ostrya carpinifolia*	Pterocallis ostryae
*O. japonica*	Mesocallis pteleae
*O. virginiana*	Macrosiphum (Neocorylobium) pseudocoryli

Key to aphids on Ostrya:-

1	SIPH long, tubular, dark, with subapical zone of polygonal reticulation. Cauda long and tongue-shaped, anal plate entire. ANT PT/BASE more than 5	….. Macrosiphum (Neocorylobium) pseudocoryli
–	SIPH as short, truncated cones. Cauda knobbed, anal plate bilobed. ANT PT/BASE 1.2 or less	…..2
2	ANT III of alata dark, with 7-14 secondary rhinaria. ANT PT/BASE 0.9-1.2	….. Mesocallis pteleae
–	ANT III of alata pale with 4-7 secondary rhinaria. ANT PT/BASE 0.3-0.6	….. Pterocallis ostryae

Ostryoderris = Aganope

Fabaceae

*Ostryopsis*	Betulaceae
*Ostryopsis davidiana*	Corylobium avellanae

*Othonna* (including Hertia, Othonnopsis)	Asteraceae
*Othonna cheirifolia*	Macrosiphum euphorbiae

Othonnopsis see Othonna

Asteraceae

Otites see Silene

Caryophyllaceae

*Otochilus*	Orchidaceae
*Otochilus porrectus*	Sitobion indicum, luteum

Use key to apterae on orchids under Cymbidium.

*Ottelia*	Hydrocharitaceae
*Ottelia alismoidis*	Rhopalosiphum nymphaeae

*Ourisia*	Plantaginaceae
*Ourisia microphylla*	Neomyzus circumflexus

Ourouparia see Uncaria

Rubiaceae

*Oxalis*	Oxalidaceae
*Oxalis acetosella*	Aphis nasturtii; Aulacorthum solani; [Hyperomyzus lactucae]; [Jacksonia papillata]; [Metopolophium frisicum]; Myzus ascalonicus, persicae; Rhopalosiphoninus staphyleae
*O. articulata*	Myzus ornatus; Neomyzus circumflexus
*O. cernua* = O. pes-caprae
*O. corniculata*	Aphis aurantii, craccivora, gossypii, nasturtii, spiraecola; Aulacorthum solani; Brachycaudus helichrysi; Macrosiphum euphorbiae; Myzus cymbalariae, ornatus, persicae; Indomasonaphis anaphalidis; Neomyzus oliveri; Neotoxoptera oliveri; Rhopalosiphoninus latysiphon, staphyleae
*O. debilis* var. corymbosa	Aphis fabae; Myzus persicae
*O. deppei*	Aphis fabae; Neomyzus circumflexus
*O. enneaphylla*	Myzus ascalonicus
*O. latifolia*	Aphis gossypii; Macrosiphum euphorbiae; [Micromyzodium filicium]; Myzus persicae
*O. laxa*	Myzus cymbalariae
*O. martiana* = O. debilis var. corymbosa
*O. oregana*	Macrosiphum sp. (Oregon, USA; BMNH collection, leg. D. Hille Ris Lambers); Rhopalosiphoninus staphyleae
*O. pes-caprae*	Aphis aurantii, craccivora, fabae, gossypii, solanella, spiraecola; Aulacorthum solani; Macrosiphum euphorbiae; Myzus persicae; Rhopalosiphoninus staphyleae
*O. purpurea*	Myzus persicae
*O. rosea*	Myzus persicae; Neomyzus circumflexus
*O. semiloba*	Aphis gossypii; Myzus persicae
*O. stricta*	Abstrusomyzus reticulatus; Protaphis middletonii
*O. trilliifolia*	Myzus ornatus, persicae
*O. variabilis* = O. purpurea
*O. versicolor*	Aphis fabae
*O. violacea* = O. debilis var. corymbosa
*Oxalis* sp.	[Rhopalosiphum maidis]

Key to apterae on Oxalis:-

1	BL 3.8-4.7 mm. SIPH pale, smooth and markedly swollen on distal 0.7 (Fig.34a). Dorsal hairs long, thick, and blunt or slightly expanded apically	…..Indomasonaphis anaphalidis
–	Without that combination of characters	…..2
2	Dorsum with an extensive solid dark sclerotic shield, with very conspicuous, dark, non-spinulose reticulation. SIPH slightly swollen near apex	…..Abstrusomyzus reticulatus
–	Dorsum with or without dark markings; if with a solid dark sclerotic dorsal shield then this either lacks reticulation, or the reticulation is either pale or finely spinulose, and SIPH are either markedly inflated over more than half of length or completely lack any trace of swelling	…..3
3	SIPH cylindrical/tapering, with polygonal reticulation on distal 0.12-0.26 of length	…..4
–	SIPH if cylindrical/tapering then without polygonal reticulation	…..go to key to polyphagous aphids
4	ABD TERG 7 and 8 mostly with spinal tubercles (STu) and ABD TERG 2-5 often with marginal tubercles (MTu)	…..Macrosiphum sp. (Oregon, BMNH collection)
–	Stu and MTu only sporadically present	…..Macrosiphum euphorbiae

*Oxybaphus*	Nyctaginaceae
*Oxybaphus angustifolius* = Mirabilis nyctaginea var. angustifolia
*O. nyctagineus*	Aphis asclepiadis, fabae; Macrosiphum euphorbiae

Use key to polyphagous aphids.

Oxycoccus see Vaccinium

Ericaceae

*Oxydendrum*	Ericaceae
*Oxydendrum arboreum*	Aulacorthum solani

*Oxylobium*	Fabaceae
*Oxylobium callistachys*	Aphis gossypii
*O. lineare*	Aphis gossypii

*Oxylobus*	Asteraceae
*Oxylobus* sp.	Aphis solitaria

*Oxypetalum*	Apocynaceae
*Oxypetalum* sp.	Aphis gossypii, nerii

Use key to polyphagous aphids.

Oxypogon see Lathyrus

Fabaceae

*Oxyria*	Polygonaceae
*Oxyria digyna*	Aphis fabae; Indomasonaphis rumicis; Nasonovia ribisnigri

Key to apterae on Oxyria:-

1	BL more than 3.5 mm. SIPH pale and strongly swollen on distal part	…..Indomasonaphis rumicis*
–	BL less than 3 mm. SIPH pale or dark, and tapering or cylindrical on distal part	…..2
2	ANT tubercles well-developed. ANT PT/BASE 7.0-11.4. Thoracic spiracles much larger than abdominal ones, with apertures rounded	…..Nasonovia ribisnigri
–	ANT tubercles weakly developed. ANT PT/BASE 1.7-3.5. Thoracic spiracles similar in size to abdominal ones, with apertures reniform	…..Aphis fabae

*Oxytropis*	Fabaceae
*Oxytropis campestris*	Acyrthosiphon churchillense; Aphis astragali; Nearctaphis vera
*O. deflexa* (incl. var. sericea)	Acyrthosiphon churchillense
*O. glabra*	Megoura viciae (ssp. turanica Nevsky 1929)
*O. hudsonica* = viscida var. hudsonica
*O. lambertii*	Aphis ?craccivora (as medicaginis)
*O. microphylla*	Aphis craccivora
*O. myriophylla*	Aphis craccivora
*O. oxyphylla*	Aphis craccae, oxytropis
*O. pilosa*	Aphis craccivora; Acyrthosiphon pisum
*O. sordida*	Aphis astragali; Nearctaphis vera
*O. viscida* var. hudsonica	Acyrthosiphon churchillense; Aphis masoni
*Oxytropis* spp.	Acyrthosiphon kondoi; Aphis oxytropiradicis, [polaris]

Key to apterae on Oxytropis:-

1	(Only al. known, but the following should also apply to apt.) Cauda as short as or shorter than its basal width in dorsal view. SIPH with transverse rows of spinules. Longest hairs on ANT III 60-70 μm, c.2.5 × BD III	…..Nearctaphis vera*
–	Cauda tongue- or finger-shaped, longer than its basal width. SIPH with normal imbrication. Longest hairs on ANT III 0.3-2.2 × BD III	…..2
2	ANT tubercles well developed, with smooth divergent inner faces. ABD TERG 1 and 7 without marginal tubercles (MTu). (SIPH without subapical reticulation)	…..3
–	ANT tubercles undeveloped or weakly developed. ABD TERG 1 and 7 with MTu	…..6
3	SIPH black, black, swollen in middle (cigar-shaped), similar in length to cauda, which is also black	…..Megoura viciae
–	SIPH mainly pale, tapering/cylindrical, longer than cauda, which is also pale	…..4
4	SIPH very attenuate distally, thinner than hind tibiae at their respective midlengths. ANT BASE VI 1.9-2.9 × R IV+V	…..Acyrthosiphon pisum
–	SIPH gradually tapering, not attenuate distally, thicker than hind tibia at their respective midlengths. ANT BASE VI 1.1-1.8 × R IV+V	…..5
5	ANT III with (2-) 4-11 rhinaria in a row on basal half. SIPH 1.2-1.6 × cauda	…..Acyrthosiphon churchillense
–	ANT III with 1 (-3) rhinaria near base. SIPH 1.6-2.1 × cauda	…..Acyrthosiphon kondoi
6	Dorsal abdomen without any sclerotisation. Large MTu consistently present on ABD TERG 2-4 as well as 1 and 7. R IV+V c. 1.5 × HT II	…..Aphis oxytropiradicis*
–	Dorsal abdomen with at least some sclerotisation. MTu absent from ABD TERG 2-4 or only sporadically present, and small. R IV+V less than 1.4 × HT II	…..7
7	Hairs on ANT III 0.3-0.75 × BD III. Dorsal abdomen usually with a solid black shield extending over all of ABD TERG 1-6. SIPH 1.2-2.2 × cauda, which bears 4-9 hairs	..…Aphis craccivora
–	Hairs on ANT III 0.8-2.2 × BD III. Dorsal abdomen with scattered or segmentally-divided black markings, or with a variably developed or fragmented black shield that does not usually extend laterally to unite with marginal sclerites on ABD TERG 1-3. SIPH 0.5-1.1 × cauda, which bears 6-16 hairs	…..8
8	R IV+V markedly narrowed subapically, with acute apex; 1.2-1.3 × HT II	…..Aphis oxytropis*
–	R IV+V tapering gradually to blunt apex; 0.8-1.1 × HT II	…..9
9	Dorsal abdomen with solid black shield extending over middle parts of ABD TERG 1-3 or 1-4 and completely across ABD TERG 4-6 or 5-6. ANT PT/BASE (1.7-)1.9-2.4	…..Aphis craccae
–	Dorsal abdominal sclerotisation variable but all tergites with at least some intersegmental division. ANT PT/BASE 1.3-1.9 (-2.0)	…..10
10	SIPH 0.50-0.65 (-0.67) × cauda	…..Aphis masoni
–	SIPH (0.65-) 0.70-1.1 × cauda	…..11
11	Dorsal abdomen with spino-pleural bars on ABD TERG 4-6 or 5-6, but ABD TERG 1-2 (-3) only ever with scattered small sclerites (Fig.16i). Cauda tongue-shaped, 0.23-0.33 mm	…..Aphis astragali
–	Dorsal abdomen variably but more evenly sclerotised. Cauda elongate triangular, 0.16-0.21 mm	…..Aphis polaris

*Ozoroa*	Anacardiaceae
Ozoroa insignis	Aphis gossypii
O. paniculosa	Aphis gossypii

*Ozothamnus*	Asteraceae
*Ozothamnus diosmifolius*	Myzus persicae
*O. leptophyllus*	[?Casimira sp. (New Zealand; see Teulon et al. 2013)]

*Pachira*	Malvaceae
Pachira spp.	Aphis craccivora, gossypii; Protaphis middletonii

Use key to polyphagous aphids.

*Pachylophis*	Onagraceae
*Pachylophis cespitosa*	Aphis oenotherae

*Pachycarpus*	Apocynaceae
*Pachycarpus lineolatus*	Aphis nerii
*P. schinzianus*	Aphis nerii

*Pachypleurum*	Apiaceae
*Pachypleurum alpinum*	Cavariella nipponica

*Pachystachys*	Acanthaceae
*Pachystachys lutea*	Aphis aurantii, gossypii; Myzus persicae

Use key to polyphagous aphids.

*Pachystima*	Celastraceae
*Pachystima myrsinites*	Wahlgreniella sp. (western USA; A. Jensen, aphidtrek.org)

*Packera* see Senecio	Asteraceae
*Packera anonyma* see Senecio anonymus
*P. aurea* see Senecio aureus
*P. cana* see Senecio canus
*P. glabella* see Senecio glabellus
*P. paupercula* see Senecio pauperculus
*P. plattensis* see Senecio plattensis
*P. tomentosa* see Senecio tomentosus

*Padus* see Prunus	Rosaceae
*Padus avium* see Prunus padus

*Paederia*	Rubiaceae
*Paederia chinensis* = P. foetida
*P. foetida* (incl. chinensis, mairei, maritima, scandens, tomentosa)	Aphis gossypii, spiraecola; Aulacorthum esakii, [myriopteroni]; Pseudomegoura nipponica
*P. scandens* = P. foetida
*P. tomentosa* = P. foetida

Key to apterae on Paederia:-

1	Head dark and densely spiculose at least on ventral surface, with ANT tubercles well-developed and steep-sided	…..2
–	Without that combination of characters	…..go to key to polyphagous aphids
2	Tergum wholly dark sclerotic. SIPH cylindrical/tapering on distal half, mainly pale/dusky, sometimes darker at base and apex. Longest hairs on ANT III more than 0.5 × BD III	…..Aulacorthum esakii
–	Tergum not wholly sclerotic, often with variably developed dark sclerites on ABD TERG 1-6. SIPH somewhat swollen on distal half, and wholly dark. Longest hairs on ANT III less than 0.5 × BD III	…..Pseudomegoura nipponica

*Paeonia*	Paeoniaceae
*Paeonia lactiflora*	Myzus persicae
*P. × suffruticosa*	Aphis gossypii, spiraecola

Use key to polyphagous aphids.

*Palaquium*	Sapotaceae
*Palaquium* sp.	Parathoracaphis setigera

*Palicourea*	Rubiaceae
*Palicourea alpina*	Aphis (Toxoptera) aurantii; Aulacorthum solani

Use key to polyphagous aphids.

*Palisota*	Commelinaceae
*Palisota ambigua*	Pentalonia nigronervosa
*P. hirsuta*	Pentalonia nigronervosa
*P. thyrsiflora* = P. ambigua

*Paliurus*	Rhamnaceae
*Paliurus spina-cristi*	Aphis frangulae, gossypii, [paliuri Lichtenstein (nomen nudum)], nasturtii, Aphis sp. (Toros et al., 2002: 31)
Paliurus sp.	[Aphis exploratus (= nasturtii?)]

Use key to aphids on Rhamnus.

*Pallenis*	Asteraceae
*Pallenis maritima*	Brachycaudus helichrysi; Protaphis terricola
*P. spinosa* = Asteriscus spinosus

Use key to apterae on Asteriscus.

*Palura* see Symplocos	Symplocaceae
*Palura chinensis* = Symplocos paniculata

*Panax*	Araliaceae
*Panax* spp.	Aphis aurantii, craccivora, odinae; Myzus persicae; [Rhopalosiphoninus latysiphon]

Use key to polyphagous aphids.

*Pandanus*	Pandanaceae
*Pandanus tectorius*	Astegopteryx pandani

*Pandiaka*	Amaranthaceae
*Pandiaka involucrata*	Aphis gossypii

*Pandorea*	Bignoniaceae
*Pandorea pandorana*	Myzus ornatus
*P. ricasoliana*	Aphis gossypii

Use key to polyphagous aphids.

Panicularia see Glyceria

Poaceae

*Panicum*	Poaceae
*Panicum adenophorum*	Sitobion neusi, [Sitobion sp. (Millar 1994)]
*P. afzelii*	Aphis gossypii
*P. antidotale*	Anoecia corni, furcata; [Colopha ulmicola? (as Rhizobius spicatus)]; Hysteroneura setariae; Rhopalosiphum maidis
*P. barbinode* = Brachiaria mutica
*P. boliviense* = Polygonum polygonatum
*P. capillare*	Anoecia corni, cornicola; Geoica setulosa; Hysteroneura setariae; Protaphis middletonii; Rhopalosiphum maidis
*P. clandestinum*	Hysteroneura setariae
*P. colonum* = Echinochloa colonum
*P. coloratum*	Rhopalosiphum maidis; [Sitobion sp. (Millar 1994)]
*P. conjugatum* = Paspalum conjugatum
*P. crus-corvi* = Echinochloa crus-galli
*P. crusgalli* = Echinochloa crus-galli
*P. decompositum*	Hysteroneura setariae
*P. deustum*	Rhopalosiphum maidis
*P. dichotomiflorum*	Anoecia corni; Rhopalosiphum maidis
*P. fasciculatum* = Brachiaria fasciculata
*P. fimbriatum* = Digitaria ciliaris
*P. flavidum* = Paspalidium flavidum
*P. germanicum* = Setaria italica
*P. glabrum* = Digitaria ischaemum
*P. glanduliferum*	Sitobion neusi
*P. glutinosum*	Hysteroneura setariae; Rhopalosiphum padi
*P. hemitomum*	Rhopalosiphum maidis
*P. hirticaule*	Tetraneura akinire
*P. infestum*	Rhopalosiphum maidis
*P. javanicum* = Urochloa panicoides
*P. laevifolium* = Panicum schinzii
*P. laxum*	Hysteroneura setariae
*P. maximum*	Hysteroneura setariae; Rhopalosiphum maidis; Sipha flava; Sitobion africanum, lambersi, [Sitobion sp. (Millar 1994)]; Tetraneura akinire
*P. miliaceum*	Anoecia corni, vagans; [Diuraphis muehlei]; Forda marginata; Geoica utricularia; Hysteroneura setariae; Melanaphis pyraria, sacchari; Myzus persicae; Neomyzus circumflexus; Paracletus cimiciformis, cimiciformis ssp. panicumi; [Prociphilus bumeliae]; Rhopalosiphum maidis, nymphaeae, padi; Schizaphis graminum; Sipha maydis; Sitobion avenae; Tetraneura akinire, caerulescens, javensis, ulmi, yezoensis
*P. montanum* = Panicum notatum
*P. muticum* = Brachiaria mutica
*P. notatum*	Hysteroneura setariae
*P. novemnerve*	Tetraneura akinire
*P. paludosum*	Brachysiphoniella montana
*P. patens* = Cyrtococcum patens
*P. pilosum*	Tetraneura akinire
*P. plicatum* = Setaria palmifolia
*P. polycaulon* = Panicum strigosum
*P. polygonatum*	Aphis gossypii; Hysteroneura setariae
*P. proliferum* = P. antidotale
*P. prostratum* = Brachiaria reptans
*P. psilopodium* = P. sumatrense
*P. purpurascens* = Brachiaria mutica
*P. repens*	Brachysiphoniella montana; Hysteroneura setariae; Schizaphis hypersiphonata; Sitobion avenae, fragariae
*P. reptans* = Brachiaria reptans
*P. sanguinale* = Digitaria sanguinalis
*P. schinzii*	Sitobion ?africanum
*P. scoparium*	Hysteroneura setariae; Tetraneura akinire
*P. sellowii*	Tetraneura akinire
*P. strigosum*	Hysteroneura setariae; Tetraneura akinire
*P. sumatrense*	Hysteroneura setariae
*P. teneriffae* = Tricholaena teneriffae
*P. trichoides*	Pseudoregma panicola
*P. trigonum* = Cyrtococcum trigonum
*P. turgidum*	Forda
*P. virgatum*	Anoecia cornicola; Rhopalosiphum maidis
*Panicum* spp.	Aphis craccivora, Aphis (Toxoptera) aurantii; Anoecia fulviabdominalis; Ceratovacuna graminum, panici; Colopha ulmicola; Diuraphis noxia; Geoica utricularia; [Kaltenbachiella nirecola]; Laingia psammae; Prociphilus erigeronensis; Sitobion miscanthi; Tetraneura ulmi

Use key to apterae of grass-feeding aphids under Digitaria.

Panzeria see Panzerina

Lamiaceae

*Panzerina* (including Panzeria)	Lamiaceae
*Panzerina lanata*	Aphis panzeriae

*Papaver*	Papaveraceae
*Papaver alpinum*	Aulacorthum solani; Rhopalosiphoninus staphyleae
*P. arenarium*	Aphis fabae
*P. argemone*	Aphis solanella; Myzus ascalonicus
*P. canescens*	Acyrthosiphon ilka
*P. croceum* = P. nudicaule
*P. decaisnei*	Acyrthosiphon ilka
*P. dubium*	Aphis fabae; Brachycaudus helichrysi; Myzus persicae
*P. glaucum*	[Lipaphis pseudobrassicae]; Myzus persicae
*P. hybridum*	Aphis craccivora, fabae, solanella
*P. laestadianum*	Aphis fabae
*P. macrostomum*	Aphis fabae
*P. nudicaule*	Acyrthosiphon ilka, [ilka ssp. montanum]; Aphis craccivora; Macrosiphum euphorbiae; Myzus persicae; Neomyzus circumflexus
*P. orientale*	Aphis fabae; Aulacorthum solani; Brachycaudus helichrysi; Macrosiphum euphorbiae, [gei]; Neomyzus circumflexus
*P. pavoninum*	Acyrthosiphon ilka; Aphis craccivora, fabae
*P. pilosum* (including ssp. strictum)	Aphis fabae, kazdagensis; Brachycaudus cardui
*P. pinnatifidum*	Aphis fabae
*P. rhoeas*	Aphis fabae, gossypii, solanella; Aulacorthum solani; Macrosiphum euphorbiae; Myzus persicae
*P. somniferum*	Acyrthosiphon ilka, [papaverinum], papaverisuctum, [titovi Mordvilko (nomen nudum)]; Aphis fabae, gossypii, [idaei], nasturtii, solanella, [triglochinis]; Brachycaudus helichrysi; [Lipaphis pseudobrassicae]; Macrosiphum euphorbiae, [stellariae]; Myzus ascalonicus, persicae; Rectinasus buxtoni; Rhopalosiphum padi; Smynthurodes betae
*P. strigosum* = P. rhoeas
*P. subpiriforme*	Macrosiphum euphorbiae
*P. tianschanicum* = P. canescens
*Papaver* spp.	[Macrosiphum stellariae]; Rhopalosiphum rufiabdominale

Key to apterae on Papaver:-

1	ANT PT/BASE less than 0.3. Body and appendages densely hairy. SIPH absent	…..2
–	ANT PT/BASE at least 0.5. Body and appendages not densely hairy. SIPH present	…..3
2	ANT V BASE and R IV+V both very long, respectively about 1.7 and 2.5 × width of head between antennal bases. ANT II similar in length to ANT I, much shorter than III	.….Rectinasus buxtoni
–	ANT V BASE and R IV+V of normal length , both about 0.5 × width of head between antennal bases. ANT II about twice as long as ANT I, similar in length to III	..…Smynthurodes betae
3	SIPH pale, long, tapering or cylindrical on distal half, and without subapical polygonal reticulation. ANT tubercles with smooth, broadly divergent inner faces, and median frontal tubercle evident	…..4
–	SIPH either not pale, long and tapering, or with subapical polygonal reticulation, and other characters not in above combination	…..5
4	SIPH 1.67-2.2 × cauda. R IV+V 0.75-0.95 × HT II	…..Acyrthosiphon ilka
–	SIPH 1.4-1.5 × cauda. R IV+V 0.69-0.77 × HT II	…..Acyrthosiphon papaverisuctum
5	Cauda helmet-shaped, somewhat constricted at base, not longer than its basal width in dorsal view. SIPH with a subapical annular incision. Spiracular apertures large and rounded	…..6
–	Cauda not helmet-shaped. SIPH without a subapical annular incision. Spiracular apertures small, usually reniform	…..7
6	Dorsal abdomen with an extensive solid black shield. ANT III 0.31-0.47 mm, 2.4-3.4 × HT II. R IV+V 0.17-0.24 mm. SIPH dark, imbricated, 1.7-3.4 × cauda	……Brachycaudus cardui
–	Dorsal abdomen without a black shield. ANT III 0.07-0.25 mm, 0.9-2.2 × HT II. R IV+V 0.10-0.15 mm. SIPH pale, smooth, 0.8-2.0 × cauda	……Brachycaudus helichrysi
7	URS with 5-6 accessory setae, 1.46–1.60 × HT II. ABD TERG IV and V each with a pair of spinopleural sclerites. Mean setal length on ANT III 0.37–0.58 × ANT III basal diameter (Kök et al. 2024)	…..Aphis kazdagensis
–	Without the above combination of characters	…..go to key to polyphagous aphids (but note that specimens running to Macrosiphum euphorbiae could be M. stellariae)

*Paphiopedilum*	Orchidaceae
*Paphiopedilum insigne*	Neomyzus circumflexus; Sitobion indicum/luteum group
*P. venustum*	Aulacorthum solani
Paphiopedilum spp.	Cerataphis orchidearum; [Pentalonia nigronervosa]

Use key to aphids on orchids under Cymbidium.

*Pappea*	Sapindaceae
*Pappea capensis*	Aphis aurantii, citricidus, gossypii

Use key to polyphagous aphids.

*Pappobolus*	Asteraceae
*Pappobolus microphyllus*	Uroleucon helianthicola, pseudambrosiae

Use key to apterae on Helianthus.

Parabenzoin see Lindera

Lauraceae

*Parageum* see Geum	Rosaceae
*P. montanum* see Geum montanum

*Parahebe*	Plantaginaceae
*Parahebe catarractae*	Myzus ornatus

*Paraixeris*	Asteraceae
*Paraixeris denticulata*	Aphis gossypii (? – on roots with eggs; Chu 1949); Hyperomyzus carduellinus; Uroleucon formosanum

Use key to apterae on Ixeris.

*Parasenecio*	Asteraceae
*Parasenecio auriculatus*	Aphis fabae; Uroleucon gobonis
*P. delphiniifolia*	Brachycaudus helichrysi
*P. hastatus* (incl. ssp. orientalis)	Aphis fabae, gossypii, [grossmannae], jacobaeae, spiraecola; Aulacorthum solani; Brachycaudus helichrysi; Uroleucon fuchuense
*Parasenecio* sp.	Aleurodaphis mikaniae

Key to apterae on Parasenecio:-

1	Body elongate oval, sclerotic dorsally, with a crenulate margin due to a continuous fringe of wax glands. SIPH as pores with raised rims. Cauda knobbed, anal plate bilobed	…..Aleurodaphis mikaniae
–	Body oval or spindle-shaped, without a marginal fringe of wax glands. SIPH tubular. Cauda tongue- or finger-shaped, anal plate entire	…..2
2	SIPH dark with polygonal reticulation on distal 0.23-0.33 of length. Cauda pale. Hind tibia with a ventral row of short peg-like hairs. Dorsal abdominal hairs long and fine-pointed (longest more than 90 μm)	..…Uroleucon fuchuense
–	Without that combination of characters	…..3
3	Abdomen with large marginal tubercles (MTu) placed on dark marginal sclerites on ABD TERG 1-4(-6) and 7. Antennae, legs, SIPH and cauda all almost entirely dark	…..Aphis jacobaeae
–	MTu absent, small or only consistently present on ABD TERG 1 and 7. Appendages variously pigmented	…..go to key to polyphagous aphids (but note that specimens running to Uroleucon compositae may be U. gobonis)

*Parathelypteris*	Thelypteridaceae
*Parathelypteris glanduligera*	Macromyzus maculata; Micromyzodium polypodii
*P. nipponica*	Macromyzus maculata

Paratropia see Schefflera

Araliaceae

*Pardanthopsis* see Iris	Iridaceae
*Pardanthopsis dichotoma* = Iris dichotoma

*Parentucellia*	Orobanchaceae
*Parentucellia latifolia*	Brachycaudus mimeuri (?), persicae; [Myzus persicae]
*P. viscosa*	Brachycaudus helichrysi, persicae

Key to apterae on Parentucellia:-

(All three species have a short, helmet-shaped cauda, somewhat constricted at base.)

–	Dorsal abdomen usually with an extensive solid black shield. Femora dark except basally. SIPH dark, 2.2-3.4 × cauda	….. Brachycaudus persicae (or mimeuri? – see text)
–	Dorsal abdomen without a black shield. Femora mainly pale. SIPH pale, 0.8-2.0 × cauda	…… Brachycaudus helichrysi

*Parietaria*	Urticaceae
*Parietaria arborea* = Gesnouinia arborea
*P. debilis*	Myzus fataunae
*P. diffusa* = P. judaica
*P. floridana*	Aphis gossypii
*P. judaica*	Aphis craccivora, fabae, gossypii, parietariae
*P. lusitanica*	Aphis parietariae
*P. micrantha* = P. debilis
*P. officinalis*	Aphis gossypii, parietariae
*P. punctata*	Aphis parietariae
*P. ramiflora* = P. judaica
*Parietaria* spp.	Myzus persicae

Key to apterae on Parietaria:-

1	ANT tubercles well developed, with inner faces parallel or convergent and strongly nodulose or spiculose. SIPH pale. ABD TERG 1 and 7 without marginal tubercles (MTu)	…..2
–	ANT tubercles weakly developed, cuticle of head not nodulose or spiculose. SIPH dark. ABD TERG 1 and 7 with MTu	…..3
2	ANT 5-segmented, with PT/BASE less than 2.5. ABD TERG 7 extended posteriorly, cowl-like	…..Myzus fataunae
–	ANT 6-segmented, with PT/BASE more than 2.8. ABD TERG 7 not extended posteriorly	…..Myzus persicae
3	Cauda with 11-24 hairs. Longest hairs on ANT III 0.8-2.2 × BD III	…..Aphis fabae
–	Cauda with 4-10 hairs. Longest hairs on ANT III 0.3-0.8 × BD III	…..4
4	Dorsal abdomen with an extensive black sclerotic shield	…..Aphis craccivora
–	Dorsal abdomen without dark markings	…..5
5	SIPH 1.0-1.5 × cauda, which bears 6-10 hairs. R IV+V 1.36-1.63 × HT II	…..Aphis parietariae
–	SIPH 1.3-2.5 × cauda, which bears 4-8 hairs. R IV+V 1.1-1.4 (-1.5) × HT II	…..Aphis gossypii

*Parinari*	Chrysobalanaceae
*Parinari curatellifolia*	Aphis gossypii

*Parkia*	Fabaceae
*Parkia roxburghii* = P. timoriana
*P. timoriana*	Aphis odinae

*Parkinsonia*	Fabaceae
*Parkinsonia aculeata*	Aphis craccivora

*Parmena* see Rubus	Rosaceae
*Parmena spectabilis* see Rubus spectabilis

*Parmentiera*	Bignoniaceae
*Parmentiera aculeata*	Aphis (Toxoptera) aurantii
*P. edulis* = P. aculeata

Parodichloa see Poa

Poaceae

*Paronychia*	Caryophyllaceae
*Paronychia argentea*	Aphis craccivora

*Parrotia*	Hamamelidaceae
*Parrotia persica*	Aphis gossypii

*Parsonsia*	Apocynaceae
*Parsonsia heterophylla*	Paradoxaphis plagianthi

*Parthenium*	Asteraceae
*Parthenium argentatum*	Rhopalosiphum rufiabdominale; Uroleucon ambrosiae ssp. lizerianum
*P. bipinnatifidum*	Uroleucon ambrosiae
*P. hysterophorus*	Acyrthosiphon bidenticola; Aphis coreopsidis, gossypii, spiraecola; Brachycaudus helichrysi; Geopemphigus sp. (Mexico, BMNH collection); Uroleucon ambrosiae, ambrosiae ssp. lizerianum, pseudambrosiae, tucumani
*P. quinquefolia* (?)	Aulacorthum solani; Rhopalosiphoninus staphyleae

Key to apterae on Parthenium:-

1	ANT PT/BASE less than 0.5. ANT V and VI with spinulose imbrication/reticulation. Eyes of 3 facets. SIPH absent. Paired spinal and marginal wax glands present	…..Geopemphigus sp.
–	ANT PT/BASE more than 1.5. ANT V and VI not spinulose. Eyes multifaceted. SIPH present. No discrete wax glands	…..2
2	ANT tubercles weakly developed, not extending forward beyond middle of front of head in dorsal view. ABD TERG 1 and 7 with or without marginal tubercles (MTu)	..…3
–	ANT tubercles moderately to well developed. ABD TERG 1 and 7 without MTu	..….5
3	Cauda helmet-shaped, somewhat constricted at base, not longer than its basal width in dorsal view, with a basal constriction. SIPH pale, smooth, with a subapical annular incision. Spiracular apertures large and rounded. ABD TERG 1 and 7 without MTu	…..Brachycaudus helichrysi
–	Cauda tongue- or finger-shaped, longer than its basal width, without a basal constriction. SIPH dark, without a subapical annular incision. Spiracular apertures small and reniform. ABD TERG 1 and 7 with MTu	…..4
4	SIPH 0.24-0.40 × BL, about twice as long as the much paler cauda. Head, ANT I, II and basal part of III very pale, contrasting with dark rest of ANT	..….Aphis coreopsidis
–	SIPH only up to 0.2 × BL. Cauda pale or dark. Head and antennal segments differently pigmented	…..go to key to polyphagous aphids, starting at couplet 22
5	ANT tubercles with smooth, divergent inner faces. SIPH dark except for basal 0.2-0.3 of length, tapering/cylindrical on distal half, with subapical polygonal reticulation extending for much less than 0.1 of length	…..Acyrthosiphon bidenticola
–	Without that combination of characters; if SIPH are mainly dark then they are either swollen distally or have polygonal reticulation on much more than 0.1 of length	…..6
6	SIPH wholly dark with polygonal reticulation on distal 0.25-0.4 of length. At least some of dorsal hairs arising from small scleroites	…..7
–	Without that combination of characters	…..go to key to polyphagous aphids, starting at couplet 4
7	SIPH usually at least 1.6 × cauda, which bears 7-12 hairs	…..Uroleucon tucumani
–	SIPH less than 1.5 × cauda, which bears 16-28 hairs	…..8
8	HT II rather long and thin, 6 or more × longer than its maximum thickness, 0.9-1.1 × R IV+V	…..Uroleucon pseudambrosiae
–	HT II less than 5 × its maximum thickness and 0.70-0.85 × R IV+V	…..Uroleucon ambrosiae

*Parthenocissus*	Vitaceae
*Parthenocissus inserta*	Aphis folsomii
*P. quinquefolia*	Aphis fabae, folsomii, illinoisensis, spiraecola; [Hysteroneura setariae]
*P. semicordata*	Greenidea parthenocissi; Neothelaxes parthenocissi, viticola; Sinomegoura citricola
*P. tricuspidata*	Aphis folsomii; Myzus ornatus; Neomyzus parthenocissi; [Sitobion akebiae]
*P. vitacea* = P. inserta

Key to apterae on Parthenocissus (except couplet 2, where only data for alatae are available):-

1	ANT 5-segmented, with ANT PT/BASE less than 1. SIPH as pores. Cauda with a midway constriction delimiting the distal part as a knob	…..2
–	ANT 6-segmented, with ANT PT/BASE more than 1.5. SIPH tubular. Cauda not knobbed	…..3
2	(Al.) ANT III with oval rhinaria arranged in a row. HT II tapering, with longest ventral hairs c.1.5 × maximum diameter of segment. ABD TERG 1-7 each with one pair of spinal hairs. ABD TERG 8 with 4 (-5) hairs	…..Neothelaxes viticola*
–	(Al.) ANT III with oval to annular rhinaria scattered over whole surface. HT II parallel-sided, with longest ventral hairs c.4 × maximum diameter of segment. ABD TERG 1-7 each with 3-6 spinal hairs, and ABD TERG 8 with 6 or more hairs	…..Neothelaxes parthenocissi*
3	SIPH 0.48-0.67 × BL and bearing numerous very long hairs. Longest hairs on ANT III more than 200 μm long, 5.5-7.6 × BD III	…..Greenidea parthenocissi
–	SIPH less than 0.3 × BL, without hairs. Longest hairs on ANT III less than 100 μm long, less than 3.5 × BD III	…..4
4	ANT tubercles well developed. ABD TERG 1 and 7 without marginal tubercles (MTu)	…..5
–	ANT tubercles weakly developed. ABD TERG 1 and 7 always with MTu	…..6
5	Dorsal abdomen with a large dark central sclerite on ABD TERG 2-4, large dark post-siphuncular sclerites present. ABD TERG 7 and 8 also heavily sclerotised, and with coarse, spinulose imbrication	…..Neomyzus parthenocissi
–	Dorsal abdomen membranous or with different sclerotisation	…..go to key to polyphagous aphids, starting at couplet 5
6	R IV+V with 8-10 accessory hairs. Cauda short and broad, about as long as its basal width, with more than 20 hairs	…..Aphis folsomii
–	R IV+V with 2 accesory hairs. Cauda much longer than its basal width, with 7-19 (-24) hairs	…..7
7	Hind tibiae wholly black. Longest hairs on ANT III 0.33-0.5 × BD III	…..Aphis illinoisensis
–	Hind tibiae mainly pale, with black apices. Longest hairs on ANT III 0.8-3.4 × BD III	…..Aphis fabae