CF Insects in general. 343 



Infe£ls 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 conllitute their nidus. Bonnet mentions forue ia- 

 flances 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 j 

 the {late of its progeny being determined by the nature 

 of the feafon. 



The nidus in which the eggs of infe£ls are depofited-, 

 is generally chofen with admirable Ikill ; being adapted 

 equally to the fecurity, warmth, and i'ublidence of the 

 future larvce that are to be reared in it. Some conftru£b 

 their nefts in the earth with great labour : others depo- 

 fite their eggs upon thofe plants, the leaves of which are 

 to iuppiy food for the nafcent brood ; while feveral of 

 the mufcse eje£l their eggs in the body of the cbryfalis 

 of other infeCls ; upon the juices of which the young 

 are nourifhed at the expencc of the defencelefs animal 

 which they devour. Inflinct is an unerring guide in di- 

 redling each of thefe animals to a nidus fitted for the pre- 

 fervation of the ova. In one inllance, the common blue 

 fly is faid to be deceived ; and that is, when it depofU's 

 its eggs upon the flower of a certain plant of a putrid 

 fmcll, miftaking it for flefii in a flate of putreiaclion. 

 There the young are no fooner quickened into life than 

 they die for want of proper food ^. 



The 



• The fkin, the noftrils, the anus, and vifcera of quadrupeds, fomc. 

 times furnifh a receptacle for iuleds; and there nature dire»5LS the paievi?: 

 animal to depoCt its eggs. 



