ENTOMOLOGY 189 



with clustered masses of lice, which now assume a brownish-orange 

 color. 



A rainy and fairly cool spring and early summer are favorable 

 to the plant-louse, because, while not checking its own multiplication 

 to any degree, and, in fact, favoring it, the conditions described pre- 

 vent its predaceous and parasitic enemies from operating to any ex- 

 tent. As a rule, therefore, the drier and warmer weather commonly 

 preceding harvest enables these natural enemies to gain the upper 

 hand and quickly exterminate the lice, and this is commonly accom- 

 plished soon enough to prevent material damage to the crop. 



No remedy is possible in case of attack by this insect, since di- 

 rect application of insecticide 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. The wheat stems or culms are sub- 

 ject to the attacks of the Iarva3 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 habit instead of subsisting parasitically on other insects. Sev- 

 eral of these species feed on wild and cultivated grasses, and several 

 others on the various small grains. The two species which are espe- 

 cially destructive to wheat are known as the wheat straw-worm and 

 the wheat Joint worm. 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 de- 

 creasing the yield. 



The Wheat Joint-Worm. This insect was long confused with 

 the joint- worm of barley, the habits of which it exactly duplicates. 

 It is a true gall insect, its presence being indicated by the oblong 

 swellings or enlargements caused by the larvae 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. 



The adult insect is a minute, black, four-winged fly, measuring 

 in length from an eighth to less than a quarter of an inch, and 

 closely resembles in appearance its own Hymenopterous parasites and 

 also the parasites of the Hessian fly and like insects. The galls usually 

 occur in groups of three or four, and sometimes in large numbers to- 

 gether, greatly deforming and weakening the stem. 



On cutting these galls open they will be found to contain when 

 mature the joint-worm larva, yellowish white in color, with its jaws 

 or mouth-parts tipped with brown. In the larval and pupal stages 

 this species resembles its ally, the straw-worm. This species is be- 



