DEVELOPMENT. 19 
appearing in autumn, laying eggs on fall wheat, the larvae feeding and 
reaching puparia prior to winter, pupating and issuing as adults in 
spring to produce the spring brood of larvae, these maturing before 
harvest and the puparia resting during the summer to produce adults 
in autumn. 
This cycle is doubtless the most universal and will apply particularly 
to a large section of winter wheat cultivation under normal seasonal con- 
ditions. It is especially the normal round in the eastern United States, 
where all the earlier studies were made, and there is no occasion to 
criticise the careful work of Chapman, Tighlman, Herrick, and Fitch. 
Nevertheless, recent studies have shown wide departures from this nor- 
mal cycle, and these variations are of the utmost importance in deter- 
mining the successful application of remedial measures. It will be in 
place, therefore, to review with considerable care the results of investi- 
gations upon this subject. 
As early as 1877 Professor Eiley called attention to the effect of the 
weather upon the abundance or ri.rity of the Hessian fly, and in 1881 
noted (in the American Naturalist, vol. 15, p. 916) the effect of drought 
upon the insect, as follows: 
It has long been known that the Hessian fly flourishes best when the chinch bug 
flourishes least; in other words, that wet weather favors it. Moisture seems essen- 
tial to the well-being of the larva. The prejudicial effect of drought has not been 
hitherto observed, that we are aware of, but was Aery noticeable the past year in 
parts of Ohio, where the puparia literally dried up. Our attention was first called 
to the general death of the insect in the "flaxseed" state by Mr. E. W. Claypole. of 
Yellow Springs, Ohio, and our observations subsequently confirmed his experience. 
The intense heat had not only desiccated the Cecidomyia, but what is still more 
remarkable, in most cases the parasites also. We should like to hear from Professor 
Cook, of Michigan, and others, whether a like result followed the severe heat and 
drought in other parts of the West. The presumption is that the mortality was 
general and that farmers may expect immunity from injury for some years to come. 
Liudemann (60), in 1887, in publishing his extended account of the 
Hessian fly discussed in considerable detail the number of generations 
and time of appearance in different parts of Russia. For central Russia, 
in the latitude of Moscow, he concludes that there are three different 
broods having well-marked periods, the flies of the spring brood issuing 
from the fore part of May to the fore part of June: those of the summer 
generation from June 19 to the 1st of August, and those of the autumn 
generation from the last of August. Farther south he notes the 
appearance of the spring generation by April 20, the summer genera- 
tion June 7, and the autumn generation July 21. 
In 1890* Professor Forbes published the following succinct statement 
regarding the observations in Illinois: 
The history of the Hessian By during the past two years exhibits anew the affect o\' 
drought upon the multiplication of that species. Many of the \\ heat fields of south- 
ern Illinois, in regions which had been free from the tly the preceding year, showed it 
sixteenth Rept. state Entomologist oi' Illinois, pp, x-xi. 
