250 



SCHOOL ENTOMOLOGY 



aphides, but only at a temperature some ten degrees higher 

 than that required by the green bug. In cool wet weather 

 the aphides increase rapidly and may become destructive 



before warmer weather enables the 

 parasites to become sufficiently 

 numerous to check them. 



All of these grain aphides multi- 

 ply in the fall on volunteer oats and 

 wheat. Their destruction in early 

 fall and the abandonment of the 

 practice of growing volunteer oats 

 in the Far South, are, therefore, of 

 prime importance for their control. 

 Where small spots of young grain 

 plants have been injured the 

 aphides may be killed by spraying 

 with a 10 per cent kerosene emul- 

 sion, soap solution one pound to 

 six gallons, or Black-leaf -40 tobacco 

 extract, one part to 900 parts of 

 water, to which should be added 

 one pound of soap to each 100 gal- 

 lons. Such spots may also be cov- 

 ered with straw and burned, or be 

 plowed under. It is of considerable 

 importance, particularly with the 

 green bug, to observe small spots 

 when injury first occurs and to 



176. Dead "green 



bugs," showing hole 

 from which the ma- 

 tured parasite of Lysi- 

 phlebus emerges. The 

 top figure shows the 

 lid still attached, but 

 pushed back; the bot- 

 tom figure shows the 

 parasite emerging. 

 Enlarged. (After 

 Webster, U, S. Dept. 

 Agr.) 



treat them so as to prevent further spread. 



141. The Hessian Fly.* The most destructive of any 

 of the insects attacking wheat is the Hessian Fly, a small 

 midge which received its name from the fact that it was first 



* Mayetiola destructor Say. Family Cecidomyiidce. 



