26 
ground, made a burrow to the root of a plant of foxtail-grass (Se- 
taria) and put the root-louse on the plant, where it was afterwards 
found by digging. Presently she took the root-louse away again to 
a new place, and finding a root of foxtail exposed in a crack of the 
earth she placed the aphis on it, and there the insect remained until 
the observation closed, 
April 23 a Harpalus caliginosus was found in an ant's (Lasius 
alienus) nest, where it was surrounded by several fragments of ants 
which it had evidently been eating. April 26 another harpalid was 
captured under a board, where it was eating ants and was sur- 
rounded by fragments of those already devoured. 
April 29 the remains of four seed-corn beetles (Agonoderiis pal- 
lipes) were seen in an ant's nest which contained about two hundred 
ants, but no root-lice. May 15 a Lasuis aliemis was found feeding 
on an earthworm. 
Systematic breeding-cage experiments, made in my insectary at 
Urbana with eggs and aphids sent in by Mr. Kelly, gave results sub- 
stantially consistent with those previously published* as to periods 
and succession of generations, but yielded a much larger number 
of young for each mother aphis than I have previously reared. The 
largest number hitherto reported was fifteen young, and the average 
reared was much less than that. This year, however, thirty-six 
adults bred between July i and September 14 produced from twenty 
to eighty-four young each, with an average of forty-one to each par- 
ent, and this may probably be accepted as the known rate of multipli- 
cation under favorable conditions. The period of development from 
birth to reproductive maturity, as shown by the birth of the first 
young, varied from seven to ten days for twenty-three specimens, the 
average being 8.4 days. The time from the appearance of the first 
young of any parent to the birth of the last young of the same 
parent varied, in thirty-six cases, from 6 to 20 days, with an average 
of 10 days, and this may be taken as the ordinary length of the 
reproductive period in midsummer under insectary conditions. 
General Discussion oe the Results (Table V.). 
The most pronounced effect of an early treatment of the soil for 
the control of the corn root-aphis was produced on the Coolidge 
farm in 1904, where disking three times and harrowing once re- 
duced the number of hills infested by ants by sixty-four per cent., 
and those infested with aphids by eighty-two per cent., and the num- 
ber of insects, both ants and aphids, by ninety-two per cent. each. 
*Eigrhteentb Rep. State Ent. 111., pp. 63-64. 
