4 
) 
3 
§ 
a 
| 
Ea, 55 
The succeeding generations are not of special economic interest 
with the exception of the last to occur—the autumnal, bisexual 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, generation originating in our breeding 
cages was born April 28, and the last on the 21st of May. Migrant 
pup were first observed May 10, and winged adults May 11. The evo- 
lution 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 observed September 16; and 
male and female were seen im 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 nevertheless to give a 
fairly full account of the number and succession of generations. Stem 
mothers very young when taken (together with eggs), April 25, and 
probably hatched the preceding day, gave birth to young May 15, making 
the period of this generation twenty-one days. Young of the second or 
migrant 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. Descendants 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 (probably of the third generation) * gave birth to young June 
24—probably of the fourth generation. From this start a continuous 
series of generations was bredt+ to September 5, all adults of each genera- 
tion 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 (seven days) ; of the seventh, July 24 (fourteen 
days) ; of the eighth, August 5 (twelve days) ; of the ninth, August 15 
(ten days) : ; of the fenine August 25 (ten days) : ; and of the eleventh, 
September 5 (twelve days). “On the 16th of September males of the 
* Other observations and collections show that these specimens may have be- 
longed 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. 
= le, 
