62 
cei\ e the wash from the remainder. I can at present only a 
count for this unquestionable fact by the very much greatd 
abundance here of young smartweed" plants, doubtless bue t 
the washing down of the seeds left on the ground in fall. Th 
seems especially likely to be the true explanation, since the di 
ference in the number of plant lice on low and high ground i 
the same field diminishes greatly or entirely disappears with th 
advent of later generations and the scattering of the win<md lie 
abroad. 
LIFE HISTORY. 
Oonoi at St a tement. The corn root aphis passes the winter a 
an egg in the earth, in corn fields or, rarely, in other ground 
where purslane grows late in fall, always, so^ far as known, onl 
m the nests of a small brown ant about an eighth of an inc' 
long, know n to science as Lasius nigor or its variety, L. nigo 
alienus. This ant is the constant companion of the root lous 
throughout the year, living in burrows among the roots of th 
corn. The aphis eggs begin to hatch about the time of th 
opening of the seed leaves of the smartweed or heartweed (Pc 
lygonum persicaria ), abundant in cultivated ground. This firs 
of the spring generations is readily distinguished by character 
of foi m and color from all that follow. Appearing usually be 
foie the corn is planted, it is dependent at first, in our region 
almost wholly upon the young smartweed plants. The roots o 
these aie laid bare by the burrows of the ants, and upon thesi 
loots, within their narrow tunnels, the lice will usually be fount 
thickly clustered. Later, if the field be not planted to corn 
our common species of pigeon-grass (Setaria) divides the atten 
tion of the lice, offering in fact, for a little time, a more succu 
lent herbage than the rapidly growing smartweed. 
The second generation begins to appear about the 1st of May 
we have one breeding-cage record of the 28th of April,—and b> 
the middle of that month may be itself mature. Many of this 
genei ation are winged, while others are without wings,* tin 
winged form first occurring about May lO.f These “migrant’ 
loot lice may live at first, like those of the preceding generation 
upon smartweed and pigeon-grass, but more commonly they an 
cransfeiied to corn by the little brown ant already 7 mentioned 
either m the same field or after they have flown to another, 
these ants not only carry from weeds to corn the root lice 
all endy in their possession, but burrow hills of corn in advance, 
eagerly seizing and conveying to their subterranean galleries 
winged root lice which come their way. 
The succeeding generations are not of special economic inter¬ 
est with the exception of the last to occur—the autumnal, bi¬ 
corn fia n ^h ioD ,i b i? rn tbe same mother in a glass tube enclosing 
other winged ept by US untl a dult, when one proved to be a^wingless aphis and th 
+ This generation is at its best from May 15 to 20 in average years in Central Illinois. 
