SB 



818 



C578 



ENT No. 12, Second Series. (Revised edition.) 



_ lited States Department of Agriculture, 



DIVISION OF ENTOMOLOGY. 



THE HESSIAN FLY. 



{Cecidomyia destructor Say.) 



, ECONOMIC IMPORTANCE AND GENERAL CHARACTERISTICS. 



The Hessian fly is one of the principal enemies of the wheat crop, 

 the minimum annual damage due to it being estimated at about 10 

 per cent of the product in the ctiief wheat-growing sections of this 

 country, which indicates an annual loss of 40,000,000 bushels and over. 

 An injury of from 50 per cent to a total failure of 'the crop is not infre- 

 quent in certain localities, and the resulting loss is proportionately 

 greater. 



The parent insect is a very fragile, dark-colored gnat or midge, about 

 ^ inch long and resembling somewhat closely a small mosquito. As 

 commonly observed, however, more or less hidden in the base of young 

 wheat plants or other small grains, the insect appears either in the form 

 of a footless maggot, or larva, or in what is known as the flaxseed state, 

 which corresponds to the chrysalis of other insects. The injury to the 

 plant is done altogether by the larva, which feeds on the tissues and 

 juices, and weakens and eventually destroys the plant. 



DISTRIBUTION. 



In common with many other of our more injurious farm pests, the 

 Hessian fly is an importation from Europe ; and the evidence points 

 very strongly to the fact of its introduction in straw brought over with 

 the Hessian troops during the war of the Revolution. It first appeared 

 in injurious numbers in 1779 in the vicinity of the landing place of 

 these troops three years before on Long Island, and has gradually spread 

 westward, following the movement of settlement and wheat culture, 

 reaching the Pacific Slope about 1884, and now practicallj- extends 

 throughout the wheat belt of the United States and Canada. It has 

 long been known on the continent of Europe, covering the wheat belt 

 from Russia eastward. It appeared in England in injurious numbers 

 in 1886, and was first thought to have been recently introduced, but has 

 since been proved to have been present long before in barley fields. In 

 1888 it was reported from New Zealand, and has since become an 

 important grain pest there, thus nearly completing the circuit of the 

 globe. 



NATURAL HISTORY AND HABITS. 



The Hessian fly is distinctively a wheat insect, l)ut will breed also in 

 barley and rye. What has been taken for this insect has, in recent 

 years, been found occasionally in timothy and several wild grasses, but 

 the insects in these cases are now known to be distinct from the Hes- 

 sian fly, and the occurrence of the latter in plants other than those first 

 named is extremely doubtful. 



