LETTERS ON ENTOMOLOGY. 25 
furnished with a singular mandible like a trident 
with its three points, lies on the leaf of a twig 
covered with the aphides, and groping about, 
soon finds one, which he transfixes with this 
trident, raises into the air and devours; thus 
rendering a great service to the tree, which, 
when cleared of its destructive visitors, is enabled 
to put forth new shoots. The most important, 
however, is the pretty little lady-bird, or coc- 
cinella, which, in the larva state, feeds entirely 
on the aphides, which, under the name of the fly, 
cause so much damage to the hops. In 1807 
the shore at Brighton, and at all the watering- 
places on the south coast, was literally covered 
with them, to the great surprise of the inhabit- 
ants, who did not know that they came from 
the neighbouring hop-grounds, where they had 
done good service in their larva state. 
The parasitical insects all lay their eggs in 
living subjects, in the larvae, the pupae, and even 
in the egg; but none are known to do it in 
perfect insects. This numerous race are called 
ichneumon flies, from their analogy to the Egyp- 
tian ichneumon, which was supposed to destroy 
the serpents, and eat the crocodile's eggs. These 
flies have a long pointed tail, with which they 
pierce a hole sufficiently deep for the egg, and it 
