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 he 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-hugs, (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 



