31 



of volunteer wheat and, second, destroy this at a time to "catch 

 the progeny of the earlier breeding flies before they have had 

 time to mature. Just what the details of this procedure should 

 be, is a question for the farmer rather than for the entomologist; 

 but I suppose that the conditions may best be met by plowing 

 the stubble rather early, to give the volunteer wheat a chance to 

 start, and then so timing the planting that this wdieat may be 

 killed by the final preparation of the soil (say with a rotary har- 

 row) just before the grain is sown for the regular crop. In other 

 words, what is wanted to give effect to this idea is a definite in- 

 terval between plowing and sowing, and a final treatment of the 

 soil such as will kill the volunteer wheat. It is not necessary 

 that either plowing or sowing should be done at any uniform 

 time, but only that the proper interval be preserved between them. 

 For more precise indications we must wait until another year has 

 given. us an opportunity to verify this season's results and to re- 

 concile, if possible, some discrepancies between our own observa- 

 tions and those of our correspondents; but the interesting fact re- 

 mains that the early breeding of the fly in volunteer wheat is a 

 weak point in its life history, of which we may reasonably hope 

 to take advantage for the overthrow of this great enemy of wheat 

 culture in Illinois.* 



• 



If it should prove to be true that a much larger percentage of 

 the fly than I have estimated continues in the stubble in midsummer, 

 we shall then simply have to revive, as an adjunct to the protective 

 measure above outlined, a preventive method already often recom- 

 mended; viz., that of using every opportunity to burn the stubble 

 after harvest and to destroy the screenings from the thresher, in 

 which such of the puparia will appear as were carried away with 

 the straw. By a general practice of these precautions, it is now 

 very likely that the Hessian fly could be in very great measure 

 controlled. 



I add two calendars summarizing in tabular form the entire 

 mass of our data respecting the life history of the Hessian fly in 

 the southern part of the State.f The first of these tables exhibits 

 the dates and localities of all our collections and observations of 

 the fly in its various stages, while the second presents an abstract 

 of the results obtained by breeding only. The numbers in paren- 

 theses on the second table in the columns devoted to imagos and 

 eggs, refer back simply to the flgures at the left of the table, and 

 indicate the original lots from which imagos and eggs were bred. 



•Fortunately the measure here recommended against the Hessian fly will be equally effective 

 against a conipanlon insect, sometimes scarcely less injiirions, viz., the wheat bulb worm, Mero- 

 myza amerua\n, since the second brood of this species occurs in volunteer wheat at substantially 

 the same period as the fly. 



•f Complete to Dec. 30, 1886. The divisions between the broods are indicated by the heavy 

 transverse lines in each column. 



