0-F INSECTS IN GENERAE. 
343 
Infeds are in general oviparous, producing eggs which 
are gradually quickened into life, by the joint influence 
of the heat of the fun, and of thofe warm fubftances 
which conftitute their nidus. Bonnet mentions fome in- 
stances in the order of diptera, in which the parent in- 
fect produces living young. The genus aphlus exhibits 
a lingular phenomenon. This animal, during fummer, 
is viviparous, but towards winter becomes oviparous $ 
the ftate of its progeny being determined by the nature 
of the feafon. 
The nidus in which the eggs of infeds are depolited, 
is generally chofen with admirable fkill ; being adapted 
equally to the fecurity, warmth, and fubfiftence of the 
future larvas that are to be reared in it. borne conftmd 
their nelts in the earth with great labour : others depo. 
fite their eggs upon thofe plants, the leaves of which are 
to fupply food for the nafcent brood : while feveral of 
the mulcre ejed their eggs in the body of the chryfaiia 
of other infeeds ; upon the juices of which the young 
are nourilhed at the expence of the defencelefs animal 
which they devour. Inftind is an unerring guide in di- 
cing each of thefe animals to a nidus fitted for the pre- 
servation of the ova. In one inftance, the common blue 
fly is faid to be deceived ; and that is, when it depofits 
Hs eggs upon the flower of a certain plant of a putrid 
fmdl, miftaking it for flefn in a Hate of putrefadion. 
There the young are no fooner quickened into life than 
they die for want of proper food *. 
The 
The flein, the noftrils, the anus, and vifeera of quadrupeds, feme. 
tUnes furnilh a receptacle for infedis; and there nature diredts the parent 
a 8imal to depolit its eggs. 
