ENTOMOLOGY 185 



feeds on the tissues and juices and weakens and eventually destroys 

 the plant. 



The Hessian fly is distinctively a wheat insect, but will breed 

 also in barley and rye. Over the bulk of the wheat area of the 

 United States there are two principal broods of the Hessian fly an- 

 nually, viz., a spring and a fall brood. There are, however, supple- 

 mental broods, both in spring and in fall, particularly in the south- 

 ern wheat areas, but in the extreme northern area of the spring wheat 

 belt there may be only a single annual brood, the progeny of the 

 spring brood passing the late summer and the winter in the flaxseed 

 state instead of developing a brood in autumn. It is possible, how- 

 ever, that in this region an autumn brood may develop in volunteer 

 spring wheat. 



Each generation is represented by four distinct states, viz., (1) 

 egg, (2)_ maggot or larva, (3) pupa or flaxseed, and (4) matured 

 winged insect. The eggs are very minute and slender, pale red in 

 color, and are usually deposited in regular rows of 3 to 5 or more on 

 the upper surface of the leaf. In the case of the spring brood they 

 are sometimes thrust beneath the sheath of the leaf, on the lower 

 joints. The number of eggs produced by a single female varies from 

 100 to 150. 



The whitish maggots hatch in from three to five days and crawl 

 down the leaf to the base of the sheath, embedding themselves be- 

 tween the sheath and stem, and develop on the substance of the 

 wheat, causing more or less distortion and bulbous enlargement at 

 the point of attack. 



In a few weeks the larva contracts into a flaxseed-like object, 

 which is the puparium. In the case of the spring brood the insect 

 remains in the flaxseed state during midsummer, yielding the perfect 

 insect for the most part in September; in the case of the fall brood 

 the winter is passed in the base of the wheat in the flaxseed condition. 



The fall brood works in the young wheat very near or at the 

 surface of the ground. The spring brood usually develops in the 

 lower joints of the wheat, commonly so near the ground as to be left 

 in the stubble on harvesting. With spring wheat the attack is some- 

 times just at the surface of the ground, as in the case of the fall 

 brood. The adults from the wintered-over flaxseed puparia emerge 

 during April and May, most numerously before the middle of the 

 latter month. The adults of the important fall brood emerge chiefly 

 during September. 



The important feature in the life history of the Hessian fly from 

 the standpoint of control is the time of emergence of the fall brood 

 or broods of adults. This arises from the fact that the chief means 

 of preventing loss from this insect is in sowing late enough in the 

 fall to avoid infestation. Unfortunately, also, it is not possible to 

 give a uniform date for seeding which may be relied on year after 

 year. 



The first indication in the fall of the presence of the fly in 

 wheat is the much darker color of the leaves and the tendency to ^tool 

 Out rather freely. This is very noticeable, and give^ the Avlicat for 



