818 AN INTROD UCTION TO ENTOMOLOGY 



pine-cone willow-gall. The larvseof this gnat do not seem to interfere 

 in any way with the development of their host, there being abundant 

 food in the gall both for the owner of the gall and for its numerous 

 guests. 



The clover-leaf midge, Dasyneura trijolii. — The leaflets of white 

 clover are sometimes infested by white or orange-colored maggots 

 which fold the two halves of the leaflet together. From one to twenty 



of these larvse may be found 

 in a single leaflet. When full 

 grown the larvag make cocoons, 

 and undergo their transforma- 

 tions within the folded leaflet. 

 In Figure 1037 an infested leaf 

 containing cocoons is repre- 

 sented natural size, also a 

 larva and an adult gnat, 

 greatly enlarged. 



The clover-flower midge, 



T,, 1 , f ., Dasyneura lesuminicola. — This 



-Ine clover-leai midge. . -^ *. . *t^i 



IS a very serious pest. The 



larvse live in the heads of 

 clover and destroy the immature seed. Different kinds of clover are 

 infested by this pest; but red clover is its chief food plant; and in 

 some parts of this country it has seemed impossible to raise clover- 

 seed on account of this insect. 



The larva of the clover-flower midge passes the winter on or 

 slightly below the surface of the ground, usually but not always, in a 

 cocoon; it changes to a pupa early in the spring, and emerges an 

 adult in late April or early May. The eggs are laid in the small green 

 clover heads, many eggs in a single head, as each larva infests a 

 single floret. The larvas mature in about four weeks, and then drop 

 to the ground to transform. Two or three weeks later a second gen- 

 eration of midges appear and lay their eggs. 



The most efflcient method of combating this pest is to make the 

 first cutting of clover early, before the first generation of midges 

 have matured, that is, early in June; the drying of the clover heads 

 will result in the destruction of the larvse in them ; and thus the second 

 crop of clover will not be infested. Care should be taken to cut at 

 the same time any clover that may be growing wild in fence-corners 

 by roadsides, or elsewhere. 



The Hessian-fly, Phytophaga destructor. — ^This is the most serious 

 pest infesting wheat in this country. The larvse live at the base of a 

 leaf between it and the main stalk, where they draw their nourish- 

 ment from the plant. There are two or three broods of this insect in 

 the course of the year. The larvse of the fall brood infest the young 

 wheat-plants near the surface of the ground. When full-grown each 

 changes to a pupa within a brown puparium, which resembles a flax- 

 seed. Here they remain throughout the winter. In the spring the 

 adult gnats emerge and lay their eggs in the sheaths of leaves some 

 distance above the ground. The irifested plants are so weakened by 



