INSECTS. 183 



insect may be said to enter on the pupa state, for after this time it 

 takes no more nourishment. The brown and leathery skin, within 

 which the maggot has changed to a pupa or chrysalis, is long egg- 

 shaped, smooth, and marked with eleven transverse lines, and mea- 

 sures one eighth of an inch in length. In this form it has been 

 commonly likened to a flax-seed. The maggots of the Hessian fly 

 do not cast off their skins in order to become pupae, wherein they 

 differ from the larvae of most other gnats, and agree with those of 

 common flies ; neither do they spin cocoons, as some of the Ceci- 

 dornyians are supposed to do. The pupa gradually cleaves from 

 the dried skin of the larva, and, in the course of two or three weeks, 

 is wholly detached from it. Still inclosed within this skin, which 

 thus becomes a kind of cocoon or shell for the pupa, it remains 

 throughout the winter, safely lodged in its bed on the side of the 

 stem, near the root of the plant, and protected from the cold by 

 the dead leaves. Towards the end of April and in the forepart of 

 May, or as soon as the weather becomes warm enough in the spring, 

 the insects are transformed to flies. They make their escape from 

 their winter quarters by breaking through one end of their shells 

 and the remains of the leaves around them. Very soon after the 

 flies come forth in the spring, they are prepared to lay their eggs 

 on the leaves of the wheat sown in the autumn before, and also on 

 the spring-sown wheat, that begins, at this time, to appear above 

 the surface of the ground. They continue to come forth and lay 

 their eggs for the space of three weeks, after which they entirely 

 disappear from the fields. The maggots hatched from these eggs, 

 pass along the stems of the wheat, nearly to the roots, become sta- 

 tionary, and turn to pupae in June and July. In this state they 

 are found at the time of harvest, and, when the grain is gathered, 

 they remain in the stubble in the fields. To this, however, as Mr. 

 Havens remarks, there are some exceptions ; for a few of the in- 

 sects do not pass so far down the side of the stems as to be out of 

 the way of the sickle when the grain is reaped, and consequently 

 will be gathered and carried away with the straw. Most of them 

 are transformed to flies in the autumn, but others remain unchanged 

 in the stubble or straw till the next spring. In the winged state, 

 these flies, or more properly gnats, are very active, and, though 

 evrj" small and seemingly feeble, are able to fly to a considerable 

 distance in search of fields of young grain. Their principal mi- 

 grations take place in August and September in the Middle States, 

 where they undergo th^ir final transformations earlier than in New 



