nated over the prairie country east of the Mississippi River and north 

 of the Ohio River, so that conditions were not favorable for the root- 

 aphis. But about that time conditions changed and corn culture 

 became dominant, necessitating the continued cultivation of large areas 

 to this latter grain for a greater or less number of consecutive years. 

 Thus this pest was brought into continually increasing' prominence, 

 and ]Mr. Walsh's observations were made about the time of what was 

 probably the beginning of its career of destructiveness. 



DESCRIPTION. 



For all practical purposes the root-aphis may be sufficiently charac- 

 terized as follows: The color is l)luish-greeu, slightly whitened by a 

 waxy I^loom. The bod}' is oval, and on the anterior part of the back 

 are two short, slender, rather conspicuous cornicles or tubes, either 

 standing erect or projecting slightly backward 

 (fig. -i). The winged female (fig. 3) has a black 

 head and brownish-black thorax, the abdomen 

 being- pale green, with about three marginal l)lack 

 spots and numerous small dark specks over the 

 surface. The antennte are dark, with paler tinge 

 at articulations, and the legs are mostly black. 

 The only form of male known is wingless, like 

 the female found on the roots. 



THE ROOT- APHIS AND THE LITTLE BROWN ANT. 



Before proceeding- further it is necessary to 



1 .1 • • , , ji.-i'-i Fig. 4. — The corn root-aphis 



describe a most important and astonishing do- ^Aphis maidi-radicis): 

 mestic condition involving the lirown ant (Lasfus wingless female. Much 

 niger'Li.^ var. americanus Emery) and the other- ^^^^^^^ ongina ). 

 wise helpless Aphis tnaidi-radicis. The presence of ants burrowing 

 about young corn plants in the field has frequently attracted the 

 attention of farmers, and damages to the crop are veiy frequently 

 attributed to them. The species under consideration is one of our 

 most al)undant and wideh' distri})utod ants, occurring in colonies of 

 from fifty to several hundred in burrows in the lields. While it is of 

 itself harmless, it is in reality responsible for all of the ravages caused 

 by the root-aphis, whose life history and habits it appears to have 

 entirely revolutionized, as will now be explained. 



LIFE HISTORY AND HABITS OF THE ROOT-APHIS. 



The normal life history of aphides in general is as follows: The win- 

 ter is passed in the egg state upon or near the plant upon which the 

 young must first subsist in spring. From these eggs there hatch young 



[Cir. 86] 



