ENTOMOLOGICAL SOCIETY OF ONTARIO. 89 



Heretofore we have told people that the fly could not exist except where fall wheat 

 was grown. Bat this can be said no longer, as the pest occurs in North Dakota and in 

 a locality where fall wheat is never sown. As the fall brood of flies emerges continually 

 earlier as we go northward, it seems to me that we must eventually reach a point where 

 it will cease to appear in autumn at all, and go over until spring, a state of afi'airs that 

 will easily account for the breeding in spring wheat in North Dakota. In other words, 

 I expect to And that nature has protected the species alike from the protracted northern 

 winter, and the equally prolonged southern summer, by varying its resting season with 

 the latitude, and, possibly, also with its proximity to the seacoast. That is, we shall find 

 the insect passing both the hot and cold seasons largely in the flaxseed stage, that Vjeing 

 the stage of development during which it is best protected from the elements and the 

 lack of" food. 



There are several good reasons why we might expect the fall brood to become extinct 

 to the north, while the spring brood continues, the principal one being that there is not 

 suificient time for the former to develop before the cold season begins. Basides, in the 

 continuity of the species it can best be spared, and I understand that it is not present in 

 England. In nearly all cases where a species is two-brooded, the spring-appeiring brood 

 of adults is the producing while the fall is the diffusing brood. The spring-appearing 

 flies are loth to leave the field in which they originated, and prefer to oviposit on the 

 tillers of the wheat plant, while the autumn-appearing adults will spread out every where 

 over the country, and will, seemingly, scent out a field of wheat at long distances. They 

 can even be drawn to very small plots in the midst of large cities. With the Aphides the 

 winged female produces fewer young, but spreads them over a larger area. In Isosoma, 

 tritici the spring brood of females has so far followed this rule in the past that their wings 

 are either entirely absent or aborted, while the summer brood, grande, has invariably 

 fully developed wings and is the diffusing brood. The Army Worm, Leucania 

 unlpuncta, is destructive through one brood only, the fall brood being far less 

 gregarious. This is also true of the Chinch Bug, Blisius leiccopterus, though 

 in Northern Indiana and Northern Ohio I find the larger parts of the adults 

 with aborted wings. The spring brood of Hessian Fly, coming as it does 

 from plants that will continue through a sufficient season for their progeny to develop, 

 has no need to migrate, while those that summer in the .stubble must necessarily change, 

 as the plants can furnish no further nourishment ; besides, diS'usion and difierentiation 

 serve in a measure, to protect from natural enemies. But, notwithstanding this, it will 

 be easily observed that the latter brood can be best dispensed with without material and 

 permanent injury to the species. This appears to me to be the state of afi'airs that we 

 may look for. I do not wish to be understood as making the unqualified statement that 

 these conditions do exist, and only hope that members of this association, located to the 

 north and to the south of the area indicated, will be able to prove either the truth or 

 fallacy of my position. We have much yet to leai-n in regard to this Hes.sian fiy, and a 

 study of it in any locality would probably develop some new features, or at least new 

 parasites. 



There are some facts connected with the two species of Isosoma, /. tritici and /. 

 hordei, that, to me at least, are rather puzzling. Unless an undermined species, found in 

 New York by Dr. Lintner, proves to be tritici, I am not aware of its occurring east of 

 the Alleghany Mountains, though it reaches west to the Pacific coast. On the other 

 hand I never saw hordei in Illinois or Indiana, nor did I find them in central Ohio, yet 

 I had not been a week in the northern part of the latter State before I found them in 

 abundance. They occur, generally, over the north portion of the State and into Michigan. 

 Is it not possible that hordei is of northern origin, where the season is too short for two 

 broods, while tritici has pushed up from the south, where the protracted vernal season is 

 favorable for the development of two broods ? I find that the hordei almost invariably 

 selects small wheat plants in which to oviposit, while the summer brood of tritici as 

 invariably selects large, thrifty stalks, usually where the plants are thin on the ground 

 but rank growing. In northern Ohio I never find hordei far below the upper joint, an 

 exceptional feature I believe, though it seems to me we might look for such a state of 

 afi'airs, as it oviposits during a season intervening bat ween the spring and summer broods 



