396 
APHIDS OF THE ROCKY MOUNTAIN REGION 
DD.—Living ‘in crescent-shaped pseudo gall formed by margin of leaf 
folded back on upperside of leaf (Fig. 429). Wings hyaline, media 
simple; hairs inconspicuous; vertex with hornlike projection in aptera. 
Stem mother living with progeny. On narrow-leaf cottonwood (Populus 
angustifolia). (p. 357).....- The Crescent-gall Poplar Aphid (Cornaphis populi) 
DDD.—Leaf folded downward on midrib. (Fig. 425, 447 and 448.) Wings 
hyaline, media simple (except usually once-branched in Asiphum pseu- 
dobyrsum); hairs not conspicuous; vertex in aptera not with hornlike 
projection. Stem mother not living with progeny. 
E.—Stem mother in almond-shaped pocket midway on midrib (Fig. 
425), progeny locating along veins of same leaf. Media once-branched 
or simple; sensoria oval-transverse, absent on VI. On Populus sar- 
genti. (p. 355)...... The Poplar Leaf-purse Aphid (Asiphum pseudobyrsum ) 
EE.—Stem mother in separate pseudo gall formed by folded leaf 
edge, on older leaf (Fig. 448). Sensoria narrow-transverse, present 
on VI in alata. On Populus occidentalis. (p. 370)...........-..::c-00--02-0000-0-=" 
ee The Folded-leaf Cottonwood Aphid (Thecabius populi-condupliftolius) 
EEE.—Stem mother in small almond-shaped pseudo gall on upperside 
of leaf, not along midrib (Fig. 447), progeny on entire under surface of 
same leaf. Sensoria narrow-transverse, absent on VI. On Populus 
tacamahacas..(Cp. 370) -sec.ccs-ceseseadaueeseensccctens cass sooues ee detee sce eee =e 
ES ee ee ee ee The Folded-leaf Tacamahac Aphid (Thecabius gravicornis) 
BB.—Living in true galls formed of leaves, petioles or twigs. Stem mother 
with four-segmented antenna; living with progeny. Wings hyaline, media 
simple; sensoria narrow-transverse. 
C.—Living in complicated bladder-like leaf gall about 80 by 50, com- 
posed of crumpled and enlarged leaf or leaves of terminal bud (Fig. 
430). Unguis in spring migrant longer than base of VI and bearing 
sensoria, in fall migrant shorter than base. (p. 358) ........-....:::cccssseceseeneceeeeees 
ee a Lie eee ee The Poplar Vagabond Aphid (Mordvilkoja vagabunda) 
CC.—Living in simple thick-walled galls. Unguis always shorter than 
base of VI and not bearing sensoria. 
D.—Living in globular gall on twig at base of petiole or occasionally 
on petiole, mouth of gall transverse, rarely with protruding lips (Fig. 
438). Sensoria usually present on all antennal segments but sometimes 
only on III, 9 to 112.) T1122) to 1255 (p. (364) 2.2..2..2k eee 
See bee en ee The Poplar Twin-gall Aphid (Pemphigus populi-ramulorum) 
439). Sensoria 2 to 5 on III, absent on IV, V and VI in spring migrant; 
primary sensoria on V and VI enlarged and containing chitinous islands. 
LID GlSstoeed 5.2 (pS G4) Perec cc cs aoc see ee aaa ek eee 
Pe Sere eared The Poplar Leaf-stem Gall Aphid (Pemphigus populi-transversus ) 
DDD.—Living in globular gall composed of petiole and leaf base. 
E.—Gall not twisted, on upperside of leaf; exit a slit on underside 
of leaf among midrib (Figs. 434 and 437). 
F.—Gall with constriction at lower third (Fig. 434). Sensoria 
oval-transverse, 3 to 6 on III, 1 to 2 on IV, absent on V and 
VI. (On narrowleaf and tacamahac poplar.) (p. 361).................... 
Se ee held REED RE, NON Tee FO ok Len We Se AIS Pemphigus monophagus 
FF.—Gall not constricted (Fig. 437). Sensoria narrow-trans- 
verse appearing annular on III, present on all antennal seg- 
ments, 5 to 10 on III. (On narrowleaf poplar.) (p. 363).............. 
Se ee es The Poplar Bullet Gall Aphid (Pemphigus populi-globuli) 
EE.—Gall twisted in appearance (Figs. 433 and 436). 
F.—Gall composed chiefly of petiole; exit a slit between petiole 
and thickened leaf base (Fig. 433). Sensoria occasionally 
anastomosing, especially on V and VI. (p. 361)..----...2...----::-:cce-e00-0* 
BAAS oe The Poplar Petiole-leaf Gall (Pemphigus juncti-sensoriatus) 
FF.—Gall composed chiefly of leaf base; exit a pinhole in 
crease between petiole and leaf base (Fig. 436). Sensoria not 
anastomosing (Fig. 436). 
G.—Sensoria on V1:35t0.6.) (pik 363 ise cescceecsereeeee eee eee 
..The Poplar Leaf-petiole Gall Aphid (Pemphigus populi-caulis) 
