PARASITE-INSECTS. 65 



Goedart, and disbelieved by Reaumur and subse- 

 quent naturalists : but we think it so very extra- 

 ordinary, that we are much inclined to think the 

 observer (T. H. of Clapham) has unwittingly fallen 

 into mistake. " Some of them," he continues, " ex- 

 ecuted the task ; but the greater part were too feeble 

 to complete it; and in the course of three days more 

 they became motionless, and gradually, one after 

 another, fell shrivelled and exhausted to the bottom 

 of the cage." Some of the clusters contained up- 

 wards of a hundred cocoons, and others not more 

 than sixty. By July 12, the perfect flies made their 

 appearance by opening a sort of lid at the end of 

 each cocoon. The flies seem to differ little, except 

 in size, from the common ichneumon of the same 

 caterpillar {Microgaster glomeratus) ; but, supposing 

 them to be in the first instance e^g parasites, they 

 must have been deposited among, not in the eggs of 

 the butterfly. 



The minuteness of some of these parasite-insects 

 may be partly conceived from the fact mentioned by 

 Bonnet, — that the egg of a butterfly, not bigger than 

 a pin's head, is sufficient to nourish several of them ; 

 for out of twenty such eggs of butterflies, a pro- 

 digious number {une quantite prodigieuse) were 

 evolved *. Few species of the plant-lice {Aphides) 

 are a great deal larger than the butterfly's eggs de- 

 scribed by Bonnet ; yet these also have a parasitical 

 enemy (Microgaster Aphidum, Spinola), which 

 plunges its eggs in their bodies; but the larva?, 

 when hatched, are by no means safe, being liable 

 to the attacks of another fly of the same family 

 (Gelis agilis, Thunberg), as Dr. Turton informs 

 us f. 



* Bonnet, GEuvres, 8vo. ii. 344. Kirby, referring to this pas- 

 sage, assigns, by mistake, only two to each egg. Introd. i. 342. 

 f Transl. of Linn. iii. 48. 



e3 



