INSECTS ATTACKING CEREAL CROPS -Cont. 



HESSIAN FLY. 

 (Cecidomyia destructor Say; Order, Diptera.) 



Diagnosis. The wheat plants turn yellow and die. In April 

 and May very small, white grubs may be found in the sheathing- 

 bases close to the ground ; in the winter small, brown, oval, flax- 

 seed-like bodies may be found in the plant near the roots. 



Description and Life-history. The adult insect is a small, black- 

 ish, two-winged fly with rather long, slender legs and beautiful, 

 feathered an tennse. The adult, however, is rarely seen. The flies of 

 each generation go through four distinct life-stages: (1) The egg, 

 (2) the larva or grub, (3) the pupa or "flax-seed," (4) the adult 

 or winged insect. In no other stage than the larval is any injury 

 done to the wheat. Professor Forbes, of Illinois, has carefully 

 studied the life-history of this pest, and the following summary 

 account of the life-history of the insect is quoted from a bulletin 

 issued by him in 1890: 



There are always two destructive generations in a single year, and 

 tinder some circumstances at least three. In fact, I have obtained evi- 

 dence that there may be even four generations which attack the wheat 

 with destructive effect, two in spring and two in autumn. The princi- 

 pal injuries, however, are done by the last autumnal and the first spring 

 generations. 



The eggs are a slender oval, about a fiftieth of an inch in length, and 

 small enough to lie lengthwise in the grooves upon the upper surface 

 of the leaf of the wheat. Those for the principal autumn brood of the 

 maggots are laid most commonly on the leaf of the young wheat. The 

 maggot hatching from these makes its way down the leaf to the base of 

 its sheath, near the root, and here this milk-white, oval, smooth larva 

 remains motionless until it gets its growth (commonly in November), 

 after which it forms a tough, smooth, dark-brown case, within which it 

 spends the winter, still in the same position. From this case (the "flax- 

 seed" above mentioned) the winged insect bursts forth about the 1st of 

 the following April, in the form of a delicate, nearly black, two-winged 

 fly or gnat, which has a very close general resemblance to a small mos- 



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