331 Mr. F. Walker's Descriptions 0/ Aphides. 



are undeveloped as is usual in wingless Aphides, but in other cha- 

 racters it resembles the winged female. The body and the l(gs 

 are bristly : the front is slightly convex in the middle, and has a 

 tubercle crowned with a tuft of bristles on each side : the body is 

 nearly spindle-shaped and often appears quite full of young ones : 

 the feelers are as long as or longer than the body ; the fourth 

 joint is very much shorter than the third ; the fifth is a little 

 shorter than the fourth ; the sixth is about half the length of 

 the fifth ; the seventh is nearly as long as the fifth ; the tips of 

 the joints from the third to the sixth are brown : the fore- legs 

 are not much shorter than the hind-legs ; the shanks are straight : 

 the nectaries are about one-twentieth of the length of the body. 



A variety of this form has the body quite round, and pale yel- 

 low : the limbs are white : the feelers are longer than the body ; 

 the fourth joint is as long as the third ; the fitth is a little longer 

 than the fourth ; the sixth is more than half the length of the 

 fifth ; the seventh is much longer than the fifth ; the tips of some 

 of the joints are black : the legs are very slender and rather short. 



Another variety has much stouter legs than usual. 



The viviparous winged female. This feeds on the leaves of the 

 birch-tree {Betula alba) from July to October, but is more scarce 

 than Aphis Betula : its colour is bright yellow, and its back is 

 slightly hairy : the forehead has a slight protuberance on each 

 side : the feelers are yellow, slender, and much longer than the 

 body ; the tips of the joints are brown ; the third joint is very 

 long ; the fourth is much shorter than the third ; the fifth is a 

 little shorter than the fourth ; the sixth is slightly clavate, and 

 about one-third of the length of the fifth ; the seventh is as long 

 as the sixth : the eyes are dark red : the mouth is yellow ; its tip 

 is brown : the nectaries are extremely short, and not more than 

 one-twelfth of the length of the body : the legs are yellow, long 

 and slender ; the feet, the knees, and the tips of the shanks are 

 brown : the wings are colourless ; the wing-ribs, the wing-brands 

 and the veins are tawny ; the tips of the latter are slightly clouded ; 

 the first and second branch-veins are more perpendicular to the 

 rib-vein than in most species of this genus ; the first is thick ; the 

 fourth is obsolete except at its tip. 



The length of the fore-chest is not less than its breadth; its sides 

 are convex : the legs are very slender ; the shanks are slightly 

 curved : the main vein begins at three-fourths of the length of 

 the wing to widen into the wing-brand which is irregularly spin- 

 dle-shaped ; the fourth vein is obsolete except at its tip ; the third 

 vein is obsolete at its source, and is forked before one-third of 

 its length and forked again before two-thirds of its length ; the 

 branches of the forks, and especially of the second fork, diverge 

 rather abruptly from each other ; the second vein is rather per- 



