1/4 PTILOTA. 



and some species of these flies (Hemerobius) render the secu- 

 rity of their young doubly secure, by placing their eggs out 

 of danger at the extremity of long and slender foot-stalks 

 (fig. 9). In like manner, the boat of eggs formed by the 

 common gnat (Culex pipiens), and the egg-pouch of the 

 Hydrous, are alike deserving of notice. But it is amongst 

 the parasitic insects that this species of instinct appears most 

 fully developed. Of this numerous instances occur amongst 

 the cuckoo-bees {Cuculina Latreille, Melecta, Epeolus, &c.), 

 Chrysididce, ChalcididcB, and especially Ichneumonidce j whilst 

 the proceedings of the bot-flies, and the instinct whereby, as 

 in the Gasterophihis equi, a particular spot upon the body of 

 an animal is selected for the reception of the egg, is most re- 

 markable. It w^ould, however, be an almost endless task to 

 detail the various modes adopted by insects in order to de- 

 posit their eggs in such situations that their progeny may be 

 sure of meeting with an ample supply of food. 



If the instinct exhibited by the parent fly be worthy of 

 observation, the number of eggs which she deposits is not 

 less interesting. Thus the queen bee produces from 40,000 

 to 50,000 eggs in the course of a year ; and supposing a 

 swarm to contain 32,256 individuals, and three swarms to 

 take place in the season, the population of a hive would in 

 a single year amount to nearly 100,000 bees; and the Aley^ 

 rodes proletella, a little homopterous insect, is said to produce 

 in a year more than 200,000 young.* A species of moth, 

 according to Lyonnet, produces in the third generation more 

 than a million of young ; and the Aphis, observed by Reaurnm* 

 and Bonnet, produced at the fifth generation 5,904,900,000 

 individuals, and there may be not less than twenty genera- 



* Kirby and Spence say. that the insect deposits this number of eg-g:s, 

 but Reaumur, from whom their statement is evidently derived, gives a 

 calculation shovFing that, from the number of generations in the course 

 of a year, one female may be the progenitor of that number of individuals. 



