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A SECOND CONTEIBUTION TO A KNOWLEDGE OF THE 

 LIFE HISTOKY OF THE HESSIAN FLY 

 (Cecidomyia destructor, Say).* 



In the valuable monograpli on tlie Hessian fly published in the 

 3d Eeport of the United States Entomological Commission (1883), 

 the following summary of the facts relating to the life history of 

 the species is given: 



"There are two broods of the fly, the first laying their eggs on 

 the leaves of the young wheat from early April to the end of 

 May, the time varying with the latitude and Aveather; the second 

 brood appearing during August and the early part of September, 

 and laying about thirty eggs on the leaves of the young winter 

 wheat. 



"The eggs hatch in about four days after they are laid. Several 

 of the maggots or larvae make their way down to the sheathing 

 base of the leaf, and remain between the base of the leaves and 

 the stem near the roots, causing the stock to swell and the plant 

 to turn yellow and die. By the end of November, or from thirty 

 to forty days after the wheat is sown, they assume the 'flaxseed' 

 state, and may, on removing the lower leaves, be found as little 

 brown, oval, cylindrical, smooth bodies; a little smaller than grains 

 of rice. They remain in the wheat until during warm weather; 

 in April the larva rapidly transforms into the pupa within its 

 flaxseed skin, the fly emerging from the flaxseed case about the 

 end of April The eggs laid by this first or spring brood of flies 

 soon hatch; the second brood of maggots lives but a few weeks, 

 the flaxseed state is soon undergone, and the autumn or second 

 brood of flies appear in August. (In some cases there may be 

 two autumn broods, the earliest August brood giving rise to a 

 third set of flies in September)." 



It was especially to test, for the latitude of Southern Illinois, 

 the details of this, the current biography of the Hessian fly in 

 America, that I commenced observations on the subject in South- 

 ern Illinois in 1883. The results thus far established show that 

 in that latitude a large percentage, at least, of the flies emerge 

 as imagos before wheat harvest or immediately thereafter (May 

 28 to June 28); that, if opportunity offers, the fly will breed 



*For a prpvions contribution, which includes an account of the parasites, see 14th Rep. St. 

 Ent. 111., pp. 38-50. 



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