62 
21. Adults were emerging in abundance from June 2 to June 
9, and on the 14th of this month were again noticed, but in 
smaller numbers. June 27 the cage was overhauled and careful 
search made for flaxseeds and larvae, but none were found. The 
cage was at this date moved out of doors and re-stocked with 
grass and flaxseeds with an identical result, as determined by 
an examination in November. These latter were the aestivating 
flaxseeds, however, and as they had not even pupated October 
20, it is probable that the imagos never emerged. 
A similar experiment, commenced June 2 with the same ma¬ 
terials, was made with red-top (Agrostis vulgaris). June 5, 9, 
and 14, flies were emerging here as in the preceding cage, and 
here, as there, none appeared later. On the 27th of June a 
careful search of everything in this cage failed to discover the 
fly in any stage. Similar attempts with blue grass (Poa pra- 
tensis), orchard grass (Dactylis glomerata), and foxtail grass 
( Setaria ), begun June 30, were equally without result, but here, 
as no adult flies were seen it is possible that none appeared. 
PRACTICAL DISCUSSION. 
The principal practical effect of this, and of foregoing work of the 
kind on the life history of the Hessian fly published in my 
earlier Reports, is to emphasize more and more the importance 
of midsummer measures for the destruction of this insect. As 
now understood the fly is to be found in the interval between 
harvest and seed-time in one of three places; it is either a flax¬ 
seed in the stubble, mostly to emerge as a winged insect in 
August or early in September; it has been carried away in the 
same stage in the straw with the harvested grain; or it is grow¬ 
ing (in the latter part of the summer) as egg, larva, or pupa 
in the volunteer wheat. 
The flaxseeds removed with the grain are but a small part of 
the whole generation. If the grain is threshed before August 1 
to 20, most of them will come through with the screenings, and 
can be destroyed by feeding, burning, or heating the latter. If 
it is not so threshed thej" will probably escape in part from the 
stack or barn as they hatch from their pupa cases, and later 
will breed in volunteer grain or early wheat. 
Those in the stubble may be destroyed by burning over the 
field, or by plowing in midsummer—by the latter proceedure 
more certainly if the ground be afterwards rolled to close the 
cracks through which the winged insect might find exit. This 
plowing and rolling (or burning, if this be resorted to) may be 
done with the best effect in July or before the middle of August. 
If it be later postponed the winged flies may begin to escape, 
to breed in volunteer wheat. I need not say that it is equally 
important that this measure be taken whether the stubble 
ground is to be sowed to wheat again or not. To leave old 
wheat ground undisturbed till fall, or, still worse, until spring 
