APHIDS INFESTING ECONOMIC PLANTS 411 
BB.—Hairs inconspicuous, short and sparse; anal plate shallowly indented; 
sensoria fewer than 10 on III of alata; body immaculate; wings hyaline. (p. 
LY ANS coeds ot He SACO: 8 hehe SOUR PBA pier Besa EAST The Walnut Aphid (Chromaphis juglandicola) 
Wheat—see Grain Crops 
Willow (Salix sp.). On leaves and bark of twigs and small limbs and 
on roots. 
A.—Frontal tubercles not exceeding vertex; antenna not longer than body. 
B.—Antenna shorter than half body; hind tarsal I trapezoidal in lateral aspect; 
. radial sector of fore wing nearly straight; cornicle mammiform; cauda rudi- 
mentary, semilunar; unguis shorter than base of VI. On bark of limbs in large 
colonies. Length 4.5 to 5.5. (p. 55)....-..--- The Giant Willow Aphid (Lachnus salignus) 
BB.—Antenna not shorter than half body; hind tarsal I triangular in lateral 
aspect; radial sector of fore wing curved; cornicle not mammiform (may be ab- 
sent) ; unguis not shorter than base of VI. j 
C.—Cornicle lacking. On roots. Yellowish brown to blackish; finely pul- 
verulent; cauda rudimentary, semilunar; unguis 1.5 times length of base; 
SENGOrlagl SitO12) ONLI cOfealatace (pe LLL) icccccsesaesseccekesye vdese sac evasabcesscocce,suscanceeoncdueeisesoc 
EPRI foe os Fee 2 Oe PRE te SOE pe The Willow Root Aphid (Fullawaya saliciradicis) 
CC.—Cornicle present. On leaves and bark of twigs and limbs. 
D.—Cornicle truncate, reticulated on distal half, not longer than base of 
VI; unguis not shorter than base of VI. 
E.—Cauda semilunar. 
F.—On bark of twigs. Body dark brown to blackish; fore wing 
Slightly smoky. (1,98) secarenctecssssca-ccsc---cp-cannc Periphyllus macrostachyae 
FF.—On bark of trunk near roots. Body not blackish; fore wing 
TIO TESTO KY Dev 1 OO) apecetttec oo case ceceeeseotscenetesaccceneess Periphyllus salicicorticis 
EE.—Cauda knobbed. On leaves and twigs. Body green, brown or 
yellow, often aptera with broad black vittae; alata with bands on 
apdomenselnmlarve COlOnTeS. (C1892 \icsse eeccat casera nerd ecerceegeencneorcceeectenccasen 
The Little Black and Green Willow Leaf Aphid (Chaitophorus viminalis) 
DD.—Cornicle vasiform or cylindrical, longer than base of VI (except 
minute in P. braggii); unguis distinctly longer than base of VI. 
E.—Cauda semilunar; antenna hairy; body yellow-brown to reddish 
brown. 
F.—Cornicle cylindrical, minute, curved medially, shorter than 
base of VI; body dull yellow to dusky brown; hairy. On roots. 
(00 Feed 0G) See Be eae ce tas Pterocomma braggli 
FF.—Cornicle swollen, not curved, longer than base of VI. On 
bark. 
G.—Cornicle swelling from base. 
H.—Cornicle broad, hardly longer than twice width, 
longer than IV, with flange, yellow-ochre; body dark 
brown, with powder which gives bluish effect. (p. 110) 
eee er or The Black Willow Aphid (Pterocomma smithiae) 
HH.—Cornicle much longer than broad, shorter than 
IV, without flange, bright orange; body dull yellow- 
brown, with pair of longitudinal rows of black areas; 
very flocculemt.s: (pp. 107) noses cot ocscnccceceerteseenececteceensrerarrensvennnnns 
A eae The Flocculent Willow Aphid (Pterocomma flocculosa) 
GG.—Cornicle with swelling after proximal third. 
H.—Cornicle swollen at middle to twice diameter of 
base, bright orange, longer than IV; body bluish to 
greenish black, with powdery areas. III .70 to .75. 
BES Veeco gntete sites irn ren eerste tae Pterocomma salicis 
HH.—Cornicle swollen slightly on distal third, 
yellowish, same length as IV; body reddish-brown; 
slightly powdery on median and intersegmental lines. 
fw oy LR LTO Goby GN) ae ce 8 oe ee ee 
Petey The Reddish Brown Willow Bark Aphid (Pterocomma 
bicolor) 
