150 
appearing brood of adults is the producing while the fall is the diffus- 
ing 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 aurunm-appearing adults will spread out everywhere 
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 dif- 
fusing brood. The Army Worm. Leucania unipuneta, is destructive 
through one brood only, the fall brood being far less gregarious. This 
is also true of the Chinch Bug. Blissus leucopterus, though in northern 
Indiana and northern Ohio I find the larger part 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 nourishrnent: besides, diffusion and differentiation serve, 
in a measure, to protect from natural enemies. But notwithstand- 
ing this, it will be easily observed that the later brood can be best 
dispensed with without material and permanent injury to the species. 
This appears to me to be a state of affairs 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 indi- 
cated, will be able to prove either the truth or fallacy of my position. 
TTe have inueh yet to learn in regard to this Hessian fly. and a study of 
it in any locality ^\ould probably develop some new features, or at 
least new parasites. 
There are some facts connected with the two species of Isosoma. I. 
tritici and I. hordei. that, to me at least, are rather puzzling. Unless 
an undetermined species, found in Xew 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 possi- 
ble that horde! is of northern origin, where the season is too short for 
two broods, while tritici has pushed up from the south, where the pro- 
tracted vernal season is favorable for the development of two broods ! 
I find that 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 
