‘THE HESSIAN FLY. ae 
Great Lakes, the farmers of the southern half of southern Michigan 
could not sow their wheat with safety earlier than the farmers of 
northern Ohio, say 50 miles to the southward. It is to be pointed 
out that while east of the Alleghenies the Hessian fly extends from 
Canada southward to central Georgia, west of the Mississippi River 
it extends from Canada southward only to northéastern Oklahoma. 
(See map, fig. 8.) Over the area east of the Mississippi River climatic 
conditions, due seemingly to latitude, have had the effect of retarding 
the development of the aduit flies in the wheat stubble and their 
consequent appearance preparatory to egg laying in the fall for a 
period covering considerably oyer one month as between southern 
Michigan and southern Georgia. As a matter of fact, humidity, or 
the lack of it, seems to be a vastly more important element in influ- 
encing the distribution and development of the Hessian fly than 
either altitude or latitude. In proof of this, during seasons when 
the wheat crop of Sumner County, southern Kansas, was in many 
cases totally destroyed by the Hessian fly, at Enid, Okla., approxi- 
mately 40 miles away to the southward, it was only by the most dili- 
gent search that occasional individuals could be found in the wheat 
fields. The country between these localities is almost exclusively 
devoted to wheat, so that there was no lack of food plants, and the 
topography of the country is very much the same, the elevation of 
Enid being almost exactly that of Wellington. Not only did this 
condition obtain in the year 1907, but 1t was practically determined 
three years earlier by Mr. George I. Reeves, who made a survey of the 
distribution of the Hessian fly in that part of the country in the fall 
of 1904. The conditions up to the present remain unchanged. 
Furthermore, as observed by Mr. HE. O. G. Kelly, with the Hessian fly 
common at Kinsley, Kans., altitude 2,164 feet, and located 36 miles 
east of Dodge City, and destructively abundant at Great Bend, eleva- 
tion 1,843 feet, 82 miles northeast of Dodge City, and at Larned, 
elevation 1,995 feet, 60 miles from Dodge City and located between 
Great Bend and Kinsley, careful search at various times by several 
assistants of the Bureau of Entomology have utterly failed to reveal 
a single individual Hessian fly in the wheat fields at Dodge City, eleva- 
tion 2,480 feet, with wheat growing continuously between this point 
and Great Bend, Larned, and Kinsley. 
In the spring of 1913 wheat plants carrying approximately 1,200 
flaxseeds of the Hessian fly were transplanted by Mr. Kelly from 
Sedgewick, Kans., to Dodge City, placed in a rearing cage with mesh 
sufficiently fine to retain the adult insects, and put in the fields April 9, 
1913, under as exact field conditions as it was possible to obtain. 
This cage was allowed to remain in place until May 22, after there had 
been ample time for the flies to emerge and oviposit, whereupon it 
