20 THE HESSIAN FLY IN THE UNITED STATES. 
in such numbers at harvest time in 1887 as to make it seem probable that the follow- 
ing crop would suffer heavily, but a severe midsummer drought following prevented 
almost entirely the growth of the volunteer grain, and very probably also dried up 
the larva? and pupa? of the fly in the field. As a consequence these neighborhoods 
in 1888 were almost absolutely free from evidence of attack, although in adjacent 
counties, where the drought was less severe, the fly was noticeably abundant in the 
fall of 1887 and in the following spring. 
Experimental sowings in 1887 and 1888, made to trace the summer history of this 
insect, failed because of the drought — in the former year completely, in the latter 
partially — only the latest planting growing. One plot, sown at Albion, Edwards 
County, July 28, started slowly, and was heavily attacked by chinch bugs and grass- 
hoppers. There no Hessian flies were detected August 24, but by September 13 larvse 
of almost all ages occurred in great abundance, and by the 18th a few had formed 
fresh puparia. Transferred to the office at Champaign and kept in the open air, the 
first imago (a female) emerged October 9, a male October 10; October 16 two more 
females appeared and another male; October 27, one female and three males. On 
the final search in the cage, made November 12, a female was found dead with eggs 
near her. Compared with our previous record, as jiresented in the Fifteenth Eeport 
and in my Office Bulletin No. 3, these data merely bring the appearance of this 
autumnal brood about ten days earlier. An attempt to secure fertilized eggs and 
rear larvae from the imagos hatched as above failed, probably because the small 
number of specimens reared and their scattered appearance prevented copulation. 
In 1891 Prof. F. M. Webster (137) published data concerning the 
unusual appearances of adults, and sums up the results as follows: 
From this it will be observed that the adult flies may emerge and oviposit under 
what we suppose to be very adverse circumstances. To what extent the eggs and 
young larva? are able to withstand such weather I have no facilities at present for 
demonstrating. The major portion of the fall brood of flies, however, emerges dur- 
ing a more favorable period, and for meteorological aid against these we can only 
look to the dry, hot weather of July and August, though to the south a portion of 
September might be included. But the straggling individuals which as I have 
proved may originate from stubble, volunteer, or even early sown grain, and which 
I myself can find no satisfactory reason for not considering either the retarded or 
accelerated individuals of either one or the other or both broods, have it in their 
power to produce a considerable progeny, which, though of themselves not a serious 
menace to the crop, yet added to those of the remaining forthcoming brood, greatly 
increase the probabilities of serious damage. For these a long mild autumn, extend- 
ing into December, would appear to be exceedingly favorable, as it would enable 
their progeny to enter winter in a comparatively hardy state, and probably produce 
late appearing larva? the following year simultaneously with or but little in advance 
of the earlier appearing adults of spring. In other words, the one winter as 
advanced puparia or unemerged adults, the other as advanced larvae or newly formed 
puparia. It appears that while the autumn usually has little effect upon the major 
portion of the fall brood, a mild October and November may emphasize the destruct- 
iveness of the pest. So far as observed by me, a damp spring, even though a cold 
one, is also favorable to the development of the insect, while dry, hot summers are 
unfavorable, and cause serious mortality to the earlier stages of the fall brood of 
adults." 
In France Dr. Paul Marchal (71) has made an extended study of the 
development of the Hessian fly, and the results of his investigations 
are of more than usual interest and importance. The studies were 
made during the years 1894 and 1895, but have only recently been 
* Bui. Ohio Agric. Exp. Sta., N. Ser., v. iv, No. 7, p. 153, 
