t^o. 6. DEPARTMENT OF AGRICULTURE. 387 



Life History. 



There are two broods of this insect each year. The adult ilies 

 usually appear iu Au<;ust aud September and lay their eggs on the 

 leaves of the little wheat plants, placing from one to twenty-five or 

 thirty eggs on a leaf and laying from one hundred to one hundred and 

 fifty eggs in all (Fig. 1, F.). The eggs are very small, reddish, oval 

 in outline (Fig. 1, C), and usually hatch in four or five days, produc- 

 ing tiny white maggots which crawl down the leaf to the stem, then 

 down between the stem and leaf shealh to the joint near the level of 

 the ground. Uere they remain, sucking the sap until cold weather 

 comes, by which time they w-ill have become about an eighth of an 

 inch long (Fig. 1, D.). They then turn brown and become the well- 

 known "flax seeds" so common in wheat fields during the winter. 

 In this condition (Fig. 1, E.) they remain till spring when changes 

 inside the ''flax seed" produce the fly which escapes to lay eggs for 

 the second or spring brood. 



The eggs of this brood are laid as before on the leaves of the wheat, 

 but usually higher than those laid in the fall, so that the maggots 

 which hatch from these eggs lie above the ground level, just above 

 the lower joints. Here they remain feeding for about a month, then 

 enter the "flax seed" stage, from which the adult flies appear in Au- 

 gust and September to lay their eggs on the young wheat plants 

 which have newly come up. 



The adult fly is about the size of a mosquito, with dusky wings 

 (Fig. 1, A, B. F.). 



Food Plants. 



The favorite food plant of the Hessian Fly is wheat, though it 

 also attacks rye and barley. In some cases it has been reported as 

 W'Orking in hay fields, but this is probably incorrect. Winter wheat 

 on which the maggots are feeding has much darker colored leaves 

 than plants unaft'ected, and tends to stool out freely causing the 

 plants at first to appear particularly healthy. Later, however, the 

 plants turn yellowish and die either in part or entirely. Injury to 

 plants in the spring is chiefly shown by a w^eakening of the stems and 

 an at least partial failure of the grain on the affected stalks to fill out. 

 The laterals — tillers — which escaped the attacks of the fall brood are 

 usually the ones injured by the spring brood. 



Enemies. 



There are several insects which prey upon the Hessian Fly. Un- 

 fortunately, they cannot be relied upon to protect the wheat, but only 

 \o somewhat reduce the loss, and methods for checking the work of 

 the fly are also necessary. 



