348 APPLIED ENTOMOLOGY 



This is the only one in a great many cases, though a few other weaker 

 veins are often present. 



The plant feeders in this group produce small galls or at least swellings 

 of the portion of the plant where they live, and one or two, by attacking 

 crop plants, are of importance to man. A number of species of the genus 

 Harmolita attack different kinds of small grains such as wheat, oats and 

 barley, and at times do considerable injury. 



The Wheat Straw-worm (Harmolita grande Riley). This insect extends from 

 New York to Colorado and from the Great Lakes to Virginia and Tennessee and 

 is also present on the Pacific Coast, but has thus far been of little importance east 

 of the Mississippi River. The adult is a tiny black insect somewhat resembling 

 an ant, with red eyes, and legs banded with yellow. One generation has wings; 

 the other is wingless. 



The winter is spent in the pupa stage in the stubble of wheat fields and the 

 adults emerge in April and May in the more northerly states; earlier in the South. 

 These are the wingless forms and are very small. They lay their eggs in the 

 wheat plants which at this time have grown only a short distance above ground, 

 and the larva feeds in the short stem, usually producing a swelling there, and 

 when full-grown it has worked its way to the crown of the plant where it entirely 

 consumes the head, thus preventing the formation of any grain. By the last of 

 May these larvse have completed their feeding and pass through a brief pupal 

 period, the adults winged in this generation emerging in early May in the 

 South, and in June in the North. These individuals fly freely and spread to other 

 fields. Eggs are now laid in this wheat, preferably well up toward the head 

 where the joints are most tender and juicy. The larvae from these eggs feed 

 and reduce the yield of wheat by consuming nourishment which would otherwise 

 go to the grain. Full growth has been obtained before the straw hardens, and 

 pupation occurs during the fall. Whether the insects will be taken off in the straw 

 or remain behind in the stubble depends on the degree of advancement of the 

 plants, and the height above ground of the cutting. 



Control. Crop rotation, raising no wheat on the same land for 2 years in 

 succession is a good treatment, as the wingless generation cannot migrate to other 

 fields. Volunteer wheat in or near such fields should of course be destroyed if 

 the rotation is to be most effective. Burning over, or plowing under of the 

 stubble is also desirable, though less effective. Winter and spring wheat should 

 never be grown near each other. 



The Wheat Joint-worm (Harmolita tritici Fitch, Fig. 364) . This is a species 

 closely related to the last, found throughout the East to the Mississippi River and 

 south to about the same limits as the other species. Its life history differs from 

 that of the Wheat Straw-worm in there being only one generation a year. Winter 

 is passed as the larva in wheat straw or in the stems of various grasses, and the 

 adults appear in May or June. Eggs are deposited as high up the wheat stems 

 as the adult can find an uncovered stem. The larvse have completed their feeding 

 by harvest-time but do not pupate until the following spring. Apparently a 

 rotation of crops, and care that waste lands, fence borders, etc., do not provide 

 grass stems in which it can breed and winter are about our only methods for the 



