THE STRAIGHT-SEAMED FLIES 



3019 



half of April. They live, however, only for a few days, and perish soon after lay- 

 ing their eggs, which amount to about eighty or a hundred. These are placed 

 separately or in pairs upon the leaves of the wheat plant, and in a short time 

 hatch, when the larvae crawl down the leaf, reach the stalk, and burrow in it to 

 take up their abode and feed upon its tissues. This does not immediately, nor 

 in a direct manner, cause the death of the plant, but, weakening its stem, renders 

 it liable to be beaten down by wind or rain, and causes it to bear inferior corn ii it 

 reached maturity. Toward the end of July the larvae are full grown, and pass 

 into the pupal stage; while at the end of August or the beginning of September the 

 adults again appear and lay their eggs on winter wheat, the larvae that are hatched 

 from these passing the winter in the pupal state and completing their development 

 in the spring. Nearly allied is the wheat midge (C. tritici), which, as its name in- 



DEVELOPMENT OP HESSIAN FLY. 



. Female enlarged and of natural size; *. Abdomen of male; c. Pupa; d. Skin of larva forming pupa case; e. 

 Larva seen in profile (the line representing its natural size); /. Larva from above (enlarged); -. Wheat 

 stalks infested with larvae. 



dicates, also attacks the wheat plant, to which it at times does great damage. The 

 female lays her eggs often in numbers not on the leaves or stems, but in the 

 heart of the blossom, and their presence either entirely prevents the formation of 

 any seed, or renders that produced of a poor kind. 



There are many other species of gall midges which attack different kinds of 

 plants, such as the willow, hawthorn, etc., but lack of space forbids further refer- 

 ence to them. One only (Miastor metroloas] demands attention on account of the 

 remarkable powers of reproduction of its larvae. In the majority of cases insects are 

 only able to reproduce their kind after attaining the adult state, the larvae being 

 merely the young modified for a free and active existence; but the larvae of this 

 midge, which are found under the bark of trees, possess the remarkable power 

 of producing within their bodies living young. These grow to a certain size at 

 the expense of their parent, whose vitals they devour, then rupture the empty 

 skin and start life on their own account. The second larvae repeat the same 



