APHIS. 
181 
of Ihe insect adhering to the leaf like a small pearl. 
Such may always be found where Aphides are in 
plenty. We have observed different species of 
Aphides to be infested with different Ichneumons. 
In general the torpid Aphis submits quietly to 
this fatal operation; but we have observed some 
of them, especially one that feeds on the Sycamore, 
which is much more agile than many of this race, 
endeavouring to avoid the Ichneumon with great 
address. There is perhaps no genus of insects 
which in their larva or maggot state feed on such 
a variet}^ of food as the Musca or Fly. There is 
scarcely a part of Nature, either animate or in- 
animate, in which they are not be met with. One 
division of them, called by Linnaeus Muscat apki- 
divorce, feeds entirely on Aphides, Of the different 
.species of aphidivorous flies, which are numerous, 
having mostly bodies variegated with transverse 
.“^tripes, their females may be seen hovering over 
])lants infested with Aphides, among which they 
deposit their eggs on the .surface of the leaf. The 
larva or maggot produced from such eggs feeds, 
as soon as hatched, on the younger kinds of Aphis, 
and as it increases in size, attacks and devours 
those which are larger. These larvae are usually 
of a pale colour, adhere closely to the leaf, along 
which they slowly glide, and are formed very 
tapering towards the head. When fully grown 
they change to a pupa or chrysalis attached to 
the leaf, from whence issues the fly. The larvae 
of these flies contribute their full share to diminish 
the despoilers of Flora. To these three kinds of 
