50 



ARTHROPODA 



forty million dollars annually. The presence of these 

 grubs in an animal produces holes in the hide and renders 

 the meat along the back unwholesome. From January to 

 June fifty per cent of the cattle received in the Union Stock- 

 yards at Chicago are thus affected. 



Hessian Fly. The Hessian fly (Cecidomyia destructor) 

 is familiar to most agriculturists through its ravages on 

 the wheat crop. It is supposed to have been introduced 

 into this country on the straw brought over by the Hessian 



troops in the Rev- 

 olutionary War. 

 Specimens for 

 study are easily 

 secured by examin- 

 ing affected wheat 

 fields in May, June, 

 July, November, or 

 December. There 



FIG. 30. Photograph of the Hessian fly, twice natural are tWO genera- 

 size. The flaxseed or pupa is at the base of a stalk , rpr 

 of wheat from which the leaves are stripped down. 1S a year. 



minute reddish eggs 



are laid in the spring on the upper surface of the leaves, 

 where a fortnight later they hatch into wormlike larvae. 

 By June they attain a length of a fourth of an inch, and 

 transform to the flaxseed or pupa between the leaves and 

 the stem at its base. The stalks affected are in an in- 

 clined or brokendown condition. The adult fly emerges 

 from the pupa case in August or September ready to ovi- 

 posit on the fall crop wherein the pupae remain during the 

 winter. This insect annually damages the wheat crop to 

 the extent of forty millions of dollars. 



