312 



APPLIED ENTOMOLOGY 



but in those localities they are very injurious pests. The usual methods of control 

 are to pasture the fields before starting a seed crop, to destroy all the midges 

 present in the heads then available : by early cutting, to dry up the heads before 

 the maggots in them have finished feeding, which in the northern districts would 

 mean cutting early in June. Sometimes, cutting the clover back between the 

 fifteenth and twenty-fifth of May will prove advantageous as the new blossoms 

 will not develop until after the adults of the first generation are gone, and will 

 have progressed beyond danger of injury by the time the adults of the second 

 generation appear. Clover so cut can be fed green to stock. 



The Hessian Fly {Phytophaga destructor Say). — This insect, which 

 like the last is one of the non-gall-making Itonididse, is a native of Europe 

 and was first noticed in this country about 1779 on Long Island, N. Y. 

 Since that time, it has spread over a large part of the United States and 



Canada and is now one of the most 

 injurious insect pests in the country, 

 often destroying wheat valued at 

 millions of dollars. It feeds on wheat, 

 barley, rye, and several other species 

 of grasses. 



Its life history differs somewhat in 

 different places, apparently being 

 modified by the different methods of 

 wheat growing. Where wheat is 

 planted in the fall, the eggs are laid 

 on the leaves of the plants soon after 

 they come up, the time varying with 

 the latitude from late August and 

 September in Michigan, to the last of 

 November or early December in 

 Georgia. The eggs are placed in ir- 

 regular rows of about half a dozen, 

 generally on the upper surface of the leaf, and each fly lays 100 to 150 in 

 all. They hatch after a few days, and the tiny pinkish or reddish maggots 

 work their way down between the leaf and the stem to a point just above 

 the joint (Fig. 329). Here they remain, sucking the sap until the 

 approach of cold weather, turning more nearly white in color. Their 

 presence at this time is at first indicated by the dark color of the leaves, 

 missing stems which would otherwise begin to show, and later, the yellow- 

 ing and death of the plants. After feeding about a month, the larva 

 pupates within its larval skin which therefore becomes a puparium and so 

 greatly resembles a flax-seed that in this condition the insect is generally 

 spoken of as being in the "flax-seed" stage. In this condition, it spends 

 the winter and the adult flies (Fig. 329) emerge in the spring ; early in the 

 South; later in the North. These now lay their eggs on the wheat and, 



Fig. 329. — Hessian Fly {Phytophaga 

 destructor Say): a, adult fly; b, wheat 

 plant affected; c, maggot. Hair lines 

 show true length of a and c. (Fro7n 

 Berlese.) 



