m 



Mr. F. Walker's Descriptions 0/ Aphides. 253 



the leaf assumes a sooty appearance, and the presence of the A])his 

 as been supposed to promote the growth of Xyloma Acerinum 

 on sycamore-leaves, but the appearance of this black shining 

 fungus seems to be occasioned by the soil and the local situa- 

 tion of the tree. This Aphis is devoured by the Coccinellce or 

 lady-birds, by the larvae of the Hemerobii or lace-winged flies, 

 nd of the Syrphidce or hawk-flies ; it is carried by the Crabronidie 

 their nests, and is there stored up as provision for the larvae. 

 'ts internal destroyers are Aphidius constrictus, a species of Allo- 

 ia, Megaspilus Carpenteri, Asaphes cenea, Cyrtogaster vulgaris, 

 'oryna clavata, and Encyrtits Atheas. Coccinella 7 -punctata, the 

 iommon lady-bird, was unusually abundant on the sycamore-trees 

 the autumn of 1847 ; the beetle was of frequent occurrence in 

 he spring, and the grubs of the succeeding generation were ex- 

 edingly numerous, and attracted public attention when they 

 sumed the final state. 



The dark colour of Aphides appears first on the tips of the 

 ielers and on the tip of each of their joints, on the tip of the 

 outh, on the head, the chest, the breast, and on the back of the 

 domen, on the tips of the nectaries, on the feet, and on the tips 

 the shanks and of the thighs, and thence spreads more or less 

 er the rest of the body and of the limbs. When the skin has 

 en just shed, the body is pale and the limbs are white. 

 The preparations of these insects in Canada balsam present a 

 iew of the internal organization, and of the parasitic larva which 

 ies in the abdomen in a cui-ved position, and by appropriating to 

 tself the food received by the parent hinders the formation of 

 e young ones, of which the winged female is rather more pro- 

 ific than is the wingless female with regard to eggs. The Aphis 

 hen very young, and some time before birth, appears to consist 

 f an almost homogeneous yolk, and resembles the egg, but is 

 luch smaller. 

 The oviparous wingless female. This form attains its full 

 owth in the beginning of October, and is distinguished by the 

 ong tail-like part of the abdomen behind the nectaries; it is 

 ellow, and has a vivid green stripe on each side of the back : 

 lere are a few black spots along the middle of the abdomen, and 

 brae short black streaks near its tip : the feelers are a little 

 borter than the body. 



1st variety. Very dark green, traversed by black bands : the 

 ip of the abdomen is dull yellow, slightly streaked with black, 

 id var. Almost black. 3rd var. Pale yellow, with a fine rose- 

 lour towards the head, and along each side of the body and 

 )out the tip of the abdomen. 4th var. Green. 5th var. Ycl- 

 w. 6th var. Buff. 7th var. Pale orange. 8th var. Brown. 

 It lays its eggs during November on the buds and on the shoots 



