Mr. F. Walker^s Descriptions Aphides. 253 
the leaf assumes a sooty appearance^ and the presence of the Aphis 
has 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 Hemerohii or lace-winged flies, 
and of the Syrp/iid(P or hawk-flies ; it is carried by the Crabronidce 
to their nests, and is there stored up as provision for the larvae. 
Its internal destroyers are Aphidius constrictus, a species of Alio- 
tria, Megaspilus Carpenteri, Asaphes cenea, Cyrtogaster vulgaris^ 
Coryna clavata, and Encyrtus Athens. Coccinella 1 -punctata, the 
common lady-bird, was unusually abundant on the sycamore-trees 
in the autumn of 1847 ; the beetle was of frequent occurrence in 
the spring, and the grubs of the succeeding generation were ex- 
ceedingly numerous, and attracted public attention when they 
assumed the final state. 
The dark colour of Aphides appears first on the tips of the 
feelers and on the tip of each of their joints, on the tip of the 
mouth, on the head, the chest, the breast, and on the back of the 
abdomen, on the tips of the nectaries, on the feet, and on the tips 
of the shanks and of the thighs, and thence spreads more or less 
over the rest of the body and of the limbs. When the skin has 
been just shed, the body is pale and the limbs are white. 
The preparations of these insects in Canada balsam present a 
view of the internal organization, and of the parasitic larva which 
lies in the abdomen in a curved position, and by appropriating to 
itself the food received by the parent hinders the formation of 
the young ones, of which the winged female is rather more pro- 
lific than is the wingless female with regard to eggs. The Aphis 
when very young, and some time before birth, appears to consist 
of an almost homogeneous yolk, and resembles the egg, but is 
much smaller. 
The oviparous wingless female. This form attains its full 
growth in the beginning of October, and is distinguished by the 
long tail-like part of the abdomen behind the nectaries; it is 
yellow, and has a vivid green stripe on each side of the back : 
there are a few black spots along the middle of the abdomen, and 
some short black streaks near its tip : the feelers are a little 
shorter than the body. 
1st variety. Very dark green, traversed by black bands : the 
tip of the abdomen is dull yellow, slightly streaked with black. 
2nd var. Almost black. 3rd var. Pale yellow, with a fine rose- 
colour towards the head, and along each side of the body and 
about the tip of the abdomen. 4th var. Green. 5th var. Yel- 
low. 6th var. Buff. 7th var. Pale orange. 8th var. Brown. 
It lays its eggs during November on the buds and on the shoots 
