SUBFAMILY APHINAE 219 
Rhopalosiphum padi (Linn.) (Kaltenbach) 
The Oat Bird-cherry Aphid 
Aphis padi Linnaeus, 1758:451 and 1761:259; Kaltenbach, 1843:74. 
Rhopalosiphum prunifoliae (Fitch) (misidentification), Palmer, 1939:345. 
Rhopalosiphum padi Rogerson, 1947:157. 
Apterous Summer Vivipara. Nymph. Medium green with orange posteriorly. Adult. 
Head and prothorax yellowish brown; remainder of body blackish green to dark olive-brown; 
without powder; body surface reticulated; appendages, cornicle and rostrum ocher: with 
dusky tips; tarsi brown to black. Body length 1.7; antenna 1-1.15, III .25-.30, IV .14-.17, V 
-10-.14, VI .08-++-.30-.38; cornicle .22-.30; hind tibia .50-.55; hairs short and inconspicuous; hind 
tarsal II .07-.09. 
Alate Vivipara. Head and thorax black; prothorax green; abdomen light green with 
darker green medially and dusky lateral areas; all appendages dusky to blackish throughout. 
Body length 1.8-2; across eyes .47; antenna 1.30-1.45, III .38-.40, IV .20-.24, V .16-.19, VI .09-+- 
.40-.43, sensoria 18-20 on III, 6-9 on IV, 1-2 on V; cornicle .22-.25; hind tibia .75-.90; hind 
tarsal II .08-.10; rostral IV-+V .10-.11, attaining 2d coxa. Fore wing with 2d fork of media 
very short to absent. Cauda parallel-sided to slightly spatulate, bearing 2-3 pairs of lateral 
hairs and a single dorsal preapical one. Cornicle slightly clavate, lightly imbricated, nearly 
smooth. Hairs pointed, short and inconspicuous. 
Collections. On wheat on leaves. Colorado: Yuma (cultured in greenhouse 
at Fort Collins) and Holyoke. Apterous viviparae Dec. 3 to Feb. 14, alate vivi- 
parae Dec. 3 (few) and Jan. 4 to Feb. 14 (abundant); rare. 
Chief Distinguishing Characters. Orange coloration posteriorly, especially in 
nymph, number of sensoria on antenna of alate vivipara, length of antenna, 
especially III and unguis and frequent absence of 2d fork of media of fore wing. 
For differences from R. fitchii see discussion under said species. 
(Not figured on account of the very close similarity to R. fitchii.) 
Rhopalosiphum poae Gillette 
Gillette’s Blue Grass Aphid 
Rhopalosiphum poae Gillette, 1908b:61; Gillette and Palmer, 1932b:485. 
Apterous Summer Vivipara. Brownish black to black; cornicle, cauda and appendages 
light to dark dusky. Body length 1.9; hind tibia 1; antenna 1.8-1.9; rostrum obtuse, attaining 
between 1st and 2d coxae. 
Alate Vivipara. Brownish black throughout; appendages dusky; cornicle and cauda 
slightly dusky. Body length 1.8; hind tibia 1.10; antenna 2-2.40. Vertex distinctly convex; 
frontal tubercles developed mesially, distinctly exceeding vertex. Secondary sensoria tuber- 
culate. Hairs distinctly capitate; .01-.015 on hind tibia. Cornicle club-shaped, with flange, 
distal hal: swollen, twice as wide at middle as hind tibia. Cauda tapering, not longer than 
broad, often appearing slightly constricted near tip. Lateral tubercles on prothorax. 
RNAI PARROT UTR RR rene 
Wary gigniammmgens 
Fig. 256. Rhopalosiphum poae 
Collections. On leaves and stems of Poa sp. Colorado: Fort Collins. Alate 
and apterous viviparae Oct. 15 to Apr. 28; rather common. 
Type. U.S.N.M., No. 41947. Paratypes, Colo. Agr. Exp. Sta. Collection. 
This species is very close to R. grabhami but differs in slightly longer an- 
tenna, shorter hairs and darker body. These differences, however, intergrade. 
The fact that both species have been found leaving their respective hosts in the 
spring as though migrating to a summer host obviates the theory that possibly 
both forms are but different generations of the same species. The decision of 
the question must await biological study. 
