WILLOW APHIDES. 593 



wider apart at their tips than at their bases ; third vein two-forked ; hind wings 

 with a subcostal and two discoidal veins, the latter very closely approximate at 

 base and divergent at tip. Thighs dark honey-yel- 

 low, broadly tipped with black ; tibipe dusky, red- 

 dish at the base. 



The honey-tubes are subobsolete. The dots on the 

 abdomen are very distinct, especially on the fully 

 grown, wingless individuals. In the intermediate 

 rows the dots are six in number, the two middle 

 ones being smaller than the others. Just behind the 



middle of the abdomen, and occupying the place of 



^, . , ,, , . /, n ,, : , Fig. 195.— Lachnus dentatus ; en- 



the two middle dots in the fourth row, is a somewhat larged After Forbea 



conspicuous black, conical protuberance, varying in 



size in different individuals, and sometimes considerably more prominent than it is 



represented in the figure. Length, two-twelfths of an inch; expanse of the wings, 



six-tenths. 



88. Chaitophorus nigrce Oestlund. 



Found by Mr. Oestlund on the leaves of Salix nigra as late as Octo- 

 ber 26. 



Winged form. — Similar to Aphis in general appearance. Entire insect with long 

 white hairs. Head black, rather straight in front. Antennse about as long as the 

 body, black except base of iii ; i and li as usual and subequal, iii longest, iva little 

 shorter, v a little shorter than iv, vi about.one-half of v, vii as long as iv, setaceous ; 

 III to V moderately cicatrized. Eyes dark reddish-brown, with a prominent tubercle. 

 Beak rather short, hardly reaching second coxae, pointed. Thorax all black, pro- 

 thorax well developed, pronotum not narrowed in the middle. Wings as usual. 

 Legs with the femora more or less blackish, and the tibiie pale. Abdomen wholly 

 black or slightly pale, brown along the sides. Honey-tubes tuberculiform, not longer 

 than broad, thickest at base, usually paler than the body, Style tubercle-like, or 

 even knobbed as jn Callipterus. Length of body .06; to tip of wings .10. 



Wingless form. — General color a dull blackish-brown. Body flat, obovate or oblong, 

 quite hairy and tubercular in young specimens, becoming smooth in full-grown. 

 Antennie about one-half the body or a little longer, pale at base, dusky towards the 

 apex; relative length of the joints as in winged form; joints with long white hairs, 

 not very numerous. Abdomen usually with the middle and the margins slightlj' 

 paler. Honey-tubes as in the above form. Length of body .06. (Oestlund.)* 



89. Ehopalosiphum salicis Monell. 



This aphid occurs on the under side of leaves of Salix lucida, S. nigra, 

 and S. habylonica. 



Winged individuals. — Head and thorax dusky ; abdomen green, with various irregu- 

 lar, darker green markings. Antennse about half as long as the body, not mounted 

 on frontal tubercle; the third and fourth joints somewhat dentate; apical joint half 

 as long again as the preceding ; third and fourth joints often subconnate. Nectaries 

 light green, reaching to the tip ; the basal portion slender, expanding at the middle 

 to twice its former diameter, and again suddenly contracted at the mouth, which is 

 furnished with the usual annulus. Tail yellowish, about one-third as long as the 

 nectaries. Length 1.52"™; to tip of wings, 3.04™™. Apterous individuals entirely 

 pale green, with two darker dorsal vittte. 



90. Chionaspis salicis (Linn.). 

 Specimens of Chionaspis fraxini received from England, states Pro- 

 fessor Comstock (Ag. Rt., 1880), are identical with C. salicis received 

 * Fourteenth Ann. Rep. Geol. and Nat. Hist. Survey Minnesota, 1886, p. 49. 

 5 ENT 38 



