Report OF the State Entomologist. 



151 



except to careful and intelligent observation. The presence of the 

 insect has in several instances first been detected at the time of thresh- 

 ing, when many of the hardened and wooden portions of the straw 

 containing the larvse, in pieces measuring from a half-inch to three 

 inches in length, are broken off, and by their weight are carried from 

 the threshing machine with the grain. 



The Fly Seldom Seen. 

 The winged insect into which the joint-worm develops, is so small 

 and delicately formed (being 

 but about one-eighth of an inch 

 in length) that it would prob- 

 ably escape notice, unless it be 

 sought for by inclosing some of 

 the infested jDieces of wheat 

 straw which has had its ordin- 

 ary winter exposure, in a tight 

 box or jar, about the middle of 

 May. During the latter part 

 of the month the imprisoned 

 insect, having attained its 

 maturity, will eat a small rotind 

 hole outward from its cell, and 

 emerge as a shining black little ^^g. ii.-Male and female of Isosoma hobdei. 



creature with four transparent, almost veinless wings, and with legs 

 entirely black or having more or less yellow on them. Dr. JPitch com- 

 pares it in general appearance to a small ant. Figure 11 represents 

 the male and female " fly," with enlargements of the abdomen and 

 antenna, which differ so conspicuously as readily to indicate the sex. 



"What the Insect is. 



It belongs to the order of Plymenoptera, of which are the bees, 

 wasps, ichneumon flies, etc., and to the family of Ghalcididce. The 

 species of this group are very numerous — • perhaps a thousand exist- 

 ing in this country alone. They are minute forms, and usually occur 

 as parasites, living, in their earlier stages, within the bodies of other 

 insects, and the family is, therefore, regarded as holding high rank 

 among our beneficial insects. The genus Isosoma, however, is an 

 exception, as its members are vegetable feeders, living upon growing 

 plants and often producing galls in them. 



Eeasoning from its family relationship, which, as a rule in the 

 insect world, is attended with a general uniformity in habits, both 

 Drs. Harris and Fitch, for some time during their simultaneous study 



