THE HESSIAN FLY. 5 
LIFE HISTORY IN REGIONS OF FALL-WHEAT GROWING. 
Throughout the fall-wheat-growing sections the fly passes the 
winter in the young wheat, mostly in the flaxseed stage, but also to 
some extent as from two-thirds to full-grown larve. It is difficult 
to estimate the number of these larve that will winter over and 
remain alive until spring, owing to the fact that it is impossible to 
determine whether they are alive or dead until 
they begin to decay. But where we have at- 
tempted to rear them, even though apparently 
alive, comparatively few adults have been ob- 
tained, though, of course, this mortality would 
probably vary somewhat with the severity of 
the weather durmeg winter. 
In spring (from March in Georgia and South 
Carolina to May in Michigan) the flies escape ; 
from the flaxseeds and deposit their eggs on Fic. 6.—The Hessian fly: Pupa- 
the wheat, and the young from these develop nee See ieee 
to flaxseeds before harvest, passing the summer _ tion.) 
in the stubble. The flies from over-wintering larve come on later, 
and it is quite probable, also, that some of the very earliest deposited 
eges may give rise to adults at about this time. Thus, owing to this 
overlapping, during some seasons and in some loc: salities, there : appears 
just before harvest baat has by some been considered a supplementary 
second generation. 
In autumn the time of appearance of adults as between North and 
South isreversed. In northern Michigan the adults of the fall genera- 
tion are abroad, under normal meteorological 
conditions, during the last days of August and 
first days of September. In Georgia and South 
Carolina, under the same conditions, it may 
be the last of November or the first of De- 
cember before they have all left the stubble. 
Thus has the species adapted itself to the 
prolonged southern summer, during which 
there is little or no food for the larve. While 
there are stragglers, the major part of the gener- 
2 ation will appear and disappear within the space 
Ce a oem ie ae of a few days, probably within a week, and the 
Greatly enlarged. (After flies, by preference, will deposit their eggs on 
oem the younger plants, those of one or two leaves 
seeming to suit them best. At this time the young larve make their 
way downward nearly or quite to the roots (fig. 10). The normal out- 
come of this generation is that the individuals reach their development 
as larvee, pass into the flaxseed stage, and pass the winter as suchon the 
young wheat plants. But here again the earliest deposited eggs may 
produce adults before the winter sets in, and the delayed individuals 
