APHIDS INFESTING ECONOMIC PLANTS 395 
B.—Body black; cornicle not shorter than V. Cauda longer than base of VI, 
spoon-shaped: bushy: - (ps b35)e:.2.- ee la eet The Bean Aphid (Aphis fabae) 
BB.—Body light green, sometimes with dusky markings; cornicle not longer 
than V; cauda not longer than base of VI, not spoon-shaped and bushy. 
C.—Cauda tapering, short and bushy, with about 6 pairs of hairs; rostral 
IV-+-V, not broad. 
D.—Sensoria 10 or more on III of alata, 8 or more in aptera. (p. 123) 
Qe SS he Th he ee ee pet tk a The Corn Root Aphid (Aphis majidi-radicis) 
CC.—Cauda spoon-shaped, bearing only 2 pairs of lateral hairs; rostral 
LVi VW ebroadss (pete?) te eee The Corn Leaf Aphid (Rhopalosiphum maidis) 
Cottonwood, Poplar and Aspen (Populus spp.) 
A.—Living exposed on leaves, twigs and bark at bases of twigs. Cornicle present 
and evident. 
B.—Cornicle elongate; cylindrical or clavate. 
C.—Cornicle longer than IV; body dark. 
D.—Body black with white patches; cornicle black, 1.5 to 2 times as 
long as IV, not swollen; cauda elongate. (p. 150).........-.....c:---ccsssssessseceeseenenes 
‘ets: A SSE Ne Me SAE as The Spotted Poplar Aphid (Aphis maculatae) 
DD.—Body bluish to dark brown; cornicle ochre yellow, swollen, 1 to 
1.5 times as long as IV; cauda semilunar, inconspicuous. (p. 110)............ 
pe eterna The Black Willow and Poplar Aphid (Pterocomma smithiae) 
CC.—Cornicle not longer than IV; body yellow-olive-green to red-brown. 
ID —Cornicle winiiormiy, cy lindricales (ps 1109) on-set se cee ees 
een eles bte The American Poplar Bark Aphid (Pterocomma pseudopopulea) 
DD.—Cornicle more or less swollen. 
E.—Cornicle 1.5 to 2 times as long as hind tarsal II or about same 
aS eL Vass neuis) 1.5) times base, of \V.L.. (p:108) 22-2 Sa 
Le ee The Reddish-brown Poplar Aphid (Pterocomma populifoliae) 
EE.—Cornicle shorter than 1.5 times length of hind tarsal II, 
shorter than IV. Unguis twice as long as base. (On Aspen). 
Ge BUD Ye: ae nt sae ork ie Sole «a ee ee -Pterocomma beulahensis 
BB.—Cornicle truncate. Living on leaves and twigs. 
C.—Veins of wings bordered; cauda semilunar. 
D.—Body of aptera greenish yellow, alata with darker bands on abdo- 
ERT mCP) Ae Dy a ask gn ee Sen ae 
Vasuereenee The Cloudy-winged Cottonwood Leaf Aphid (Periphyllus populicola) 
DD.—Body dark green to shining black in aptera, abdomen light green 
with heavy bands in alata. (On Aspen, rarely on cottonwood.) (p. 97) 
YO The Black Cloudy-winged Poplar Leaf Aphid (Periphyllus bruneri) 
CC.—Veins of wings not bordered; cauda knobbed. 
D.—Body of aptera pale green; alata without distinct dark. bands on 
abdomen; sensoria 2 to 7 on III, 0 on IV in alata. (p. 90) -......-....cceceseceeesess 
=the Bets ise The Clear-winged Cottonwood Leaf Aphid (Chaitophorus populellus) 
DD.—Body of aptera pale green, alata with distinct bands on abodmen; 
sensoria 9 to 14 on III, 0 to 4 on IV in alata. (On Aspen.) (p. 92).........-.. 
echo ie Vale De The Clear-winged Aspen Leaf Aphid (Chaitophorus popylifoliae) 
AA.—Living in galls or pseudo galls or rosette leaf formations. Cornicle inconspicu- 
ous, a mere pore or absent. 
B.—Pseudo galls or simple folded or bent leaves. Stem mother with five-seg- 
mented antenna. 
C.—Living in rosette formed by backward curved leaves. Wings hyaline, 
media once-branched; hairs inconspicuous; vertex in aptera not with horn- 
like projection. Stem mother on petiole, progeny on unexposed side of 
leaves. On aspen (Populus tremuloides) (p. 355) ..---------s---s-s-sesescesnssssenseeeeeeseneeeteee 
ces eee eS Ane Se ee The Aspen Rosette Aphid (Asiphum rosettei) 
CC.—Living in simple pseudo gall composed of a single folded leaf. 
D.—Leaf folded pocketlike, with edges folded under. (Figure 427.) 
Wings slightly clouded, media once-branched; hairs prominent on ap- 
pendages; vertex in aptera not with hornlike projection. Stem mother 
living with progeny. On aspen (Populus tremuloides). (p. 356)....-.--..----.--- 
Rocke asap ee AS sts 2 a a Le The Aspen Leaf-pocket Aphid (Asiphum sacculi) 
