26 
NO REMEDY. 
No remedy is possible in case of attack by this insect, since direct 
application of insecticides to growing grain is out of the question, 
and there are no mechanical means of destroying the lice. One can 
only await the providence of the weather conditions and the action of 
natural enemies. As already pointed out, in the great majority of 
seasons, and often when the lice appear in the spring in numbers, 
unfavorable weather and the natural enemies effectually prevent 
appreciable damage. 
THE WHEAT STRAW-WORMS. 
(Isosoma tritici Fitch. ) 
(Isosoma grande Riley.) 
The wheat stems or culms are subject to the attacks of the larvee of 
certain minute insects belonging to the parasitic groups of the order 
Hymenoptera, which is represented 
by the parasites of the Hessian fly, 
plant-lice, etc. This little group 
or subfamily to which these wheat 
species belong has diverged from 
the great mass of its allies and 
acquired a strictly vegetable feed- 
ing or phytophagic habit instead 
of subsisting parasitically on other 
FIG. 12.—The wheat joint-worm (Jsosoma tritici): a Several of these species 
Adult fly, much enlarged (reduced from feed on wild and culti- 
Howard). vated erasses, and sey- 
eral others on the various small grains. The two species 
which are especially destructive to wheat are known as the 
wheat straw-worm (/sosoma grande Riley) and the wheat 
joint worm (/sosoma tritict Fitch). (Fig. 12.) The habits 
of these two insects are similar and result in similar 
injuries to the wheat crop, namely, weakening the stems 
or culms and causing them to break and fall before the 
grain is ripe, and at the same time weakening the plants 
and decreasing the yield. (Fig. 13.) 
THE WHEAT JOINT-WORM ( Jsosoma tritici Fitch). 


Fic. 13.—Wheat 
This insect was long confused with the joint-worm of oe eee 
barley (/. horde Harris), the habits of which it exactly — joint-worm 
duplicates. It is a true gall insect, its presence being pee ias  * 
indicated by the oblong swellings or enlargements caused Riley). 
by the larvee in the walls of the wheat stems. The galls are commonly 
found at or near the joints, and more commonly the second joint, but 
may occur in the vicinity of nearly every joint on the stem. 
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