450 The Enemies of the Wheat Fly. 



all the specimens lie has examined, he is of opinion that the male 

 only becomes pure white with age, the female never. 



Its habits during the breeding season, such as the construction 

 of its nest, period of incubation, &c., do not appear to be well 

 known. 



ARTICLE. LX.— TAe Enemies of the Wheat Fly. 



The life of an insect consists of several stages. The parent fly 

 lays an Qgg, and from that Qgg is hatched a worm, which after a 

 period of existence more or less extended, according to the species, 

 makes a sort of retrograde step, if we may so speak, in the journey 

 of vitality and becomes a thing, which often more resembles an 

 egg than the perfect insect intended to be finally produced. In 

 this, the'pupa state, the little animal is neatly enveloped in a membra- 

 neous shell, and remains for a time without sustenance or motion, 

 but all the time undergoing a natural process, whereby in the end 

 the gaudy butterfly, the hard- winged beetle, or the terrible wheat 

 fly, is slowly but surely elaborated : and each of these again, after 

 enjoying the sweets of insect life for a while, lays its egg and dies ; 

 thus completing the circle. 



There is more than this, however, to excite our admiration. As 

 in most instances the parent dies before its young is hatched, and 

 as with many species the larva, immediately upon its exit from the 

 Qgg^ requires a particular kind of food, without a supply of which 

 it must inevitably perish ; there can be little doubt but that if this 

 be not previously provided, the series of events would be abruptly 

 broken ofl" by the death from starvation of the new born insect. 



In these cases where the mother can never see her progeny, 

 how is she to know what kind of food it will require ? We do 

 not yet know enough of nature to answer that question. Of this 

 much only we are quite certain. The parent always seeks out a 

 mass of provision of the proper sustenance, and lays her egg either 

 in or near it, so that when the latter is hatched, the little helpless 

 worm that comes forth, has only to open its mouth and eat. 

 Thus the Hessian Fly deposits her egg on the blade of the wheat 

 plant, perhaps the only plant whose juices will nourish her young, 

 making this selection she is guided by some pre-real, the 

 nature of which is as yet unknown to the most profound 

 metaphysicians. And when the larva comes forth, guided by 

 another instinct, it immediately scrambles away straight down the 



