63 
sexual brood, by which the eggs are laid. Both males and 
females of this brood are wingless, and live in the earth like 
their parents, occurring there from the middle of September to 
the middle of November. The eggs which they lay are taken in 
charge by their attendant ants and cared for during the winter. 
Number of Generations— The eggs of the corn root louse begin 
to hatch as early as April 10, this process continuing, according 
to our observations, until May 2. The adults of this earliest 
generation, the so-called stem mothers, were first seen by us 
April 28, and the last appeared in our collections exactly one 
month later. The first of the second, or so-called migrant, gen¬ 
eration originating in our-breeding cages was born April 28, 
and the last on the 21st of May. Migrant pupae were first ob¬ 
served May 10, and winged adults May 11. The evolution of 
winged forms of this second generation has continued unques¬ 
tionably until June 2, and possibly until June 8. Our earliest 
date for the bisexual brood is September 12, when an oviparous 
female was found in a breeding cage. The first male was ob¬ 
served September 16; and male and female were seen in copula 
October 1. Living females of this brood have been taken by us 
from ants’ nests as late as December 11 (1893). Our autumnal 
dates for the collection of eggs are October 21, November 5 and 
20, and December 11. 
Our numerous breeding cage experiments, although not one 
of them is continuous throughout the year, enable me never¬ 
theless to give a fairly full account of the number and succes¬ 
sion of generations. Stem mothers very young when taken 
(together with eggs), April 25, and probably hatched the pre¬ 
ceding day, gave birth to young May 15, making the period of 
this generation twenty-one days. A'oung of the second or mi¬ 
grant generation born May 9 became winged adults May 28, 
thus requiring for their growth a period of nineteen days. 
In another case, young of the same generation born May 17 
acquired wings June 4, the interval being eighteen days. De¬ 
scendants of this migrant generation (the third of the series 
consequently) born June 8, were adult June 19 (eleven days), 
giving origin on that date to young of the fourth generation, 
which became adult on the 30th of June—again an interval of 
eleven days. Examples brought in from the field June 22 (prob¬ 
ably of the third generation)* gave birth to young June 24— 
probably of the fourth generation. From this start a contin¬ 
uous series of generations was bredt to September 5, all adults 
of each generation being in every case removed and destroyed 
by us before their young had begun to breed. Assuming that 
this experiment began with the fourth generation, the first of 
the fifth were born July 3 (nine days); of the sixth, July 10 
* Other observations and collections show that these specimens may have belonged to 
the fourth or even the fifth generation. They can hardly have been of earlier date than the 
third. 
+ These root lice were maintained thus continuously on the leaves of the corn, for 
greater convenience and accuracy of observation. 
