Over the bulk of the wheat area of the United States there are two 

 principal broods of the Hessian fly annually, viz, a spring and a fall 

 brood. There are, however, supplemental broods, both in spring and 

 in fall, particularly in the southern 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, however, 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) mature 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 between 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 sometimes 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 chieflj^ during September. 



There is a supplemental spring brood following the main one and a 

 supplemental fall brood preceding the main one. These supplemental 

 broods, however, are comparatively unimportant, most of the indi- 

 viduals of the spring and fall broods going through the course of devel- 

 opment first indicated; Under exceptional conditions the insect may 

 remain dormant in the flaxseed state for a year or more and still bring 

 forth the adult, a provision of nature which is doubtless intended to 

 prevent the accidental extermination of the species. The migrating 

 and scattering brood of adults is the one developed in the fall; the 

 spring brood does not wander much from the field in which it is 

 developed. 



EFFECT ON WHEAT. 



The first indication in the fall of the presence of the fiy in wheat is 

 the much darker color of the leaves and the tendency to stool out 

 rather freely. This is very noticeable and gives the wheat for the time 

 being a very healthy appearance. The leaves are also broader, but the 

 upright central stems are wanting, having been killed by the fly. Later, 

 the infested plants turn yellow or brown and die in part or altogether. 



