ENTOMOLOGY. 
71 
different stages are four in number, that of egg, larva, 
pupa, and imago or perfect insect. 
All insects are, strictly speaking, oviparous. The 
few instances which might be supposed to prove that 
this is not universally the case, are more apparent 
than real deviations from the general law. Certain 
two- winged flies, cocci, ground-bugs, ( Cimicidce ,) 
and aphides, give birth to larvae ; the forest-flies of 
the singular genus Hippobosca, and its near allies, 
enter the world in the pupa state. The larvae in 
question, however, are not developed in a uterus by 
means of a placenta, like the embryos of true vivi- 
parous animals, but come from eggs hatched within 
the body of the mother ; while the forest-flies, besides 
being hatched in the same manner, likewise pass the 
penultimate stage of their life, which is probably of 
very short duration, in the matrix of the parent. 
These two tribes, therefore, may be said to be ovo- 
viviparous. 
The eggs of insects do not often fall under our 
observation, on account of their small size, and being 
carefully concealed, by a variety of ingenious devices, 
that they may not fall a prey to birds and other 
enemies. Their most common situation, at least 
with such as produce herbivorous larvae, is on the 
leaves designed to serve these larvae as food ; at other 
times they are placed in fissures of wood, made by 
an instrument specially designed for the purpose, 
and not unfrequently in fruits and grain ; many are 
deposited in the earth, and not a few in water. They 
are placed either singly or in groups. Their defence 
