PARASITE, APHIDIUS TESTACEIPES. 115 
during the summer of 1907, while making observations on the life 
history of the species; hence, a series of experiments was begun in 
order to learn something definite in regard to it. Seven female 
Aphidius were selected, just as they issued from their cocoons (being 
therefore unfertilized), and placed in separate cages with 30 to 40 
Toxoptera not previously exposed to parasite attack. All of the 
parasites began ovipositing at once. After one of the females had 
apparently parasitized all of the aphidids in her cage she was mated 
and placed in a second cage with a number of Toxoptera as before. 
All the offspring from unmated females were males, but the offspring 
from the single female, after she had mated, comprised 22 females 
and 4 males. 
Messrs. Kelly and Urbahns elucidated this phenomenon more fully 
during the summer of 1908 at Wellington, Kans. 1 These experi- 
ments were conducted as follows : 
Starting with a mated female, the females from among her off- 
spring were isolated, even before emergence. On their appearance 
they were given Toxoptera not previously exposed to parasitic attack. 
The few females from among this second generation were again 
isolated in the same manner, the females in all cases being kept 
unmated. Nearly 100 experiments were conducted in this manner, 
but only 48 gave results. The offspring of 44 out of the 48 isolated 
were, all of them, males. Of the 4 remaining females, the offspring 
of 3 were as follows : 70 males and 3 females; 101 males and 6 females; 
67 males and 1 female. In the case of the remaining female, some 
uncertainty exists as to whether she had been fertilized or not, and, 
for this reason, a census of her offspring is not here included. 
Of the three exceptional cases the offspring from one female were 
not bred any further; from- a second, the offspring became all males 
in the second generation; the offspring from the third female produced 
two females in the second generation, all finally becoming males in 
the third generation. 
In this manner it will be seen that Messrs. Kelly and Urbahns were 
able to rear a limited number of females parthenogenetically to the 
third generation. Beyond this all of the offspring were males. While 
the conditions under which these experiments were conducted would 
not obtain under ordinary field conditions where the infestation was 
great, it could very easily occur where there are very few aphidids 
present. This apparently abnormal feature, then, would greatly 
assist the species in tiding over periods of scarcity of plant-lice. 
HOSTS OP APHIDIUS TESTACEIPES. 
Since we were able to find Aphidius testaceipes over almost the entire 
United States, it seemed clear to us that it must have hosts other than 
Toxoptera graminum. Accordingly Messrs. Kelly and Urbahns con- 
i Ann. Ent. Soc. Ainer., vol. 2, No. 2, 1909, pp. G7-87. 
