X 
insect, so helpful under conditions favorable to their develop¬ 
ment, has made it seem worth while to treat them at some 
length in this Report. 
Closely following upon this temporary relief of the cerea] 
crops from the worst of their hitherto generally known insect 
enemies, came an attack upon small grain by a species of Aphk 
or plant louse, well enough known to entomologists as a 
European importation of long residence here, but rarely observed 
by farmers in Illinois. This grain louse or oat louse. 
Siphonophora avense, (Plate II., Fig. 2 and 4,) began to at 
tract attention in 1889, not long after wheat harvest, when 
first in Southern and then in Central and Northern Illinois, it 
appeared in innumerable myriads on the leaves and heads of grow 
ing and ripening wheat, seriously threatening the crop, which, u{ 
to that time, had been an unusually promising one. Seasonable 
rains and favorable weather generally so sustained the grair 
plant under this attack that, as a rule, no appreciable loss 
resulted either to wheat or oats, except on thin and some 
what exhausted soils; and with the end of the wheat harvesl 
the louse practically disappeared for the season. The follow¬ 
ing year, however, it reappeared early in Southern anc 
Central Illinois as an oats insect, and the weather being 
now as unfavorable in the southern part of the State as 
it had been favorable the year before, the worst injury was 
inflicted upon agriculture ever done in Illinois by any plani 
louse species. Many hundreds of fields of oats in the sou then 
part of the State were completely destroyed while the plants 
were a few inches high; but farther north the numbers of th< 
insects were fewer and the weather was more favorable, so thai 
little or no harm resulted. 
A second species of grain louse (Toxoptera gramhium), re 
ported by Dr. Riley* as particularly destructive in Missouri anc 
Southwestern Illinois, has occurred in our observations onb 
occasionally and in small numbers with Siphonophora a vena 
in the central part of the State. 
The fruit bark beetle (Plate I.) was first detected by us in tb 
summer of 1888 at Albion, in Edwards county, and an articl 
presenting existing knowledge of the spebies was read before th 
State Horticultural Society at its meeting in that year an< 
published in its annual Transactions. Upon this followed ; 
general report of its presence, previously unsuspected, through 
out a large part of the most important fruit-growing region o 
the State, and it is now evident that this insidious insect ha 
been some time at work, has apparently already done mucl 
harm, and threatens far greater in a region where fruit cultur 
is rapidly expanding and has already become the dominant ir 
terest. A full account of this matter is given later. 
The Hessian fly has exhibited its usual susceptibility t< 
weather conditions, increasing in number with the comparative! 
* “Insect Life,” Vol. III., p. 126 . 
