208 
The “flaxseeds” of the second generation affect the wheat in the 
late spring and summer; but are situated higher up, an inch or two 
above the surface of the ground, at the lower joints of the straw. 
“In the ordinary course of nature, therefore [says Fitch], our crops 
of winter wheat are liable to two attacks of the Hessian-fly, one 
generation reared at its roots producing another, which occupies the 
lower joints of the stocks. Thus the larvae and pupae are present in it 
almost continually from the time the tender young blades appear 
above the ground-in the autumn till the grain ripens and is harvested 
the next summer. Our spring wheat, on the other hand, can rear 
but one brood of these insects; they consequently resort to it but 
little, if at all. Nor can the Hessian-fly sustain itself except in 
districts where winter wheat is cultivated in which for it to nestle 
during the autumn and winter.” 
As a general rule, then, there are two broods of the fly, the first 
laying their eggs late in April and in May, and the second brood of 
flies ovipositing* in August, during September, and perhaps a few 
early in October. Sometimes the flies_ appear earlier, as Professor 
Cook, who observed the insect in Michigan, says that “in July and 
August the flies again issue forth, and the cycle of changes for the 
year is complete. Thus we see the flies are ready for work in the 
fall, much before the v T heat is ready for them, and may attack a 
volunteer crop long before the usual crop is above ground or even 
sown.” 
A third brood may sometimes appear, as shown bv Mr. B. Hulick, of 
Michigan. According to Professor Cook, Mr. Hulick found the empty 
“flaxseeds” on volunteer wheat in September. On Professor Cook’s 
expressing some doubt whether the fly had issued, suggesting that it 
might be the parasite that had eaten the fly and come forth, as the 
time appeared to him too short, Mr. Hulick at once planted some 
of the-volunteer wheat, still containing the “flaxseed,” in close jars, 
and— 
“Saw many of the flies issue; and, more, had eggs laid by these 
flies on the same vdieat in October. Mr. Hulick showed these flies 
and their eggs to several of his neighbors. In this case the eggs 
were deposited in July, the flaxseed state assumed in September, 
from which came a third brood of flies in October. This is certainly 
a very important matter, as it shows that three broods are possible 
under favorable conditions; that while the fall flies may, nay gen¬ 
erally must, wait till September to deposit eggs, they only want 
opportunity to breed their mischief much earlier, even in July or 
August, and thus propagate a late brood of flies, which will be in 
readiness for even the latest sov T n vdieat. No doubt, too, as in the 
case of all insects, varying degrees of heat or cold will accelerate 
or retard the various transformations. (Lecture, etc., p. 9.)” 
Mode of egg-laying (see Plate I, e, the fly of its natural size en¬ 
gaged in laying its eggs on the leaf of vdieat). The mode of ovi- 
position has thus been described by Dr Herrick: 
*Mr. F. S. Sleeper writes us that he has, on one occasion, seen the Hessian Flies laying 
their eggs as late as October 26. In February, 1878, during very mild weather, he observed 
them laying their eggs. See his statements farther on. 
