INSECTS INJURIOUS TO AGRICULTURE. 193 



sheathing base of the leaf, and remain between the base of 

 the leaves and the stem near the roots, causing the stalk to 

 swell and the plant to turn yellow and die. By the end of 

 November, or from thirty to forty days after the wheat is 

 sown, they assume the "flaxseed" state, and may, on re- 

 moving the lower leaves, be found as little brown, oval, 

 cylindrical, smooth bodies, a little smaller than grains of 

 rice. They remain in the wheat until during warm weather; 

 in April the larva rapidly transforms into the pupa within 

 its flaxseed skin, the fly emerging from the flaxseed case 

 about the end of April. The eggs laid by this first or spring 

 brood of flies soon hatch; the second brood of maggots live 

 but a few weeks, the flaxseed state is soon undergone, and 

 the autumn or second brood of flies appears in August. (In 

 some cases there may be two autumn broods, the earlier 

 August brood giving rise to a third set of flies in Sep- 

 tember. ) 



There are several destructive ichneumon parasites of the 

 Hessian fly, whose combined attacks are supposed at times 

 to destroy about nine-tenths of all the flies hatched. Of 

 these, the most important is the Chalcid four-winged fly, 

 Semiotellus (Merisus) destructor (Fig. 237, ?', much en- 

 larged), which infests the flaxseed; and the egg-parasite, 

 Platygaster lierrickii Pack. 



REMEDIES. By sowing a part of the wheat early, and, if affected 

 by the fly, ploughing and sowing the rest after September 20, the 

 wheat-crop may in most cases be saved. It should be remembered 

 that the first brood should be thus circumvented or destroyed in 

 order that a second, or spring, brood may not appear. 



If the wheat be only partially affected, it may be saved by 

 fertilizers and careful" cultivation ; or a badly damaged field of 

 winter wheat may thus be recuperated in the spring. 



Pasturing with sheep, and consequent close cropping of the win- 

 ter wheat in November and early December, may cause many of the 

 eggs, larvae, and tiaxseeds to be destroyed; also, rolling the ground 

 may have nearly the same effect. 



Sow hardy varieties. The Underhill Mediterranean wheat, and 

 especially the Lancaster variety, which tillers vigorously, should be 

 sown in preference to the slighter, less vigorous kinds in a region 

 much infested by the fly. The early (August) sown wheat might 

 be Diehl; the late sown, Lancaster or Clawson. 



Of special remedies, the use of lime, soot, or salt may be recom- 

 mended, also raking off the stubble; but too close cutting of the 



