INSECTS INJURIOUS TO SMALL GRAINS 



151 



antenna) black, of the shape shown in Fig. 112. The winged 

 female is slightly larger, with a wing expanse of about one- 

 quarter inch, ancLof the same general coloration, except that the 

 head is brownish-yellow and the lobes of the thorax are blackish. 

 The aphides hatching from the eggs are all females, which give 

 birth to live young, no male forms occurring during the summer. 

 During her life of slightly over a month a female will give birth to 

 50 or 60 young, which commence to reproduce in the same manner 



FIG. 110. The spring grain-aphis or "green bug" (Toxoptera gramimum): 

 a, winged migrant; b, antenna of same, a, much enlarged; b, highly 

 magnified. (From Pergande, U. S. Dept. Agr.) 



when about seven days old, so the numbers of the pest obviously 

 increase with enormous rapidity, and with thousands of tiny beaks 

 pumping out the sap the young grain plants soon succumb. The 

 rate of reproduction and growth is, of course, much slower in 

 colder weather, the above being the average for the growing season. 

 Thus in an open winter the aphides will continue to multiply, and 

 by February', in northern Texas, small spots of wheat and oats 

 will show the effect of their work, by March the injury may become 

 widespread and serious, and by the middle of April the crops may 

 be ruined. As the aphides become excessively abundant and the 



