478 
Journal of Agricultural Research ‘ 
Vol. VII, No. n 
low temperature. One oviparous female became adult in 9 days indoors. 
Another, bom the same day and kept outdoors, developed in 12 days. 
The age at oviposition, therefore, would be from 14 to 20 days, depend¬ 
ing upon the temperature and the presence of the males. The eggs are 
deposited on the leaves of the plant and on the sides of the cage. 
FECUNDITY OF OVIPAROUS FEMALES 
The largest number of eggs produced by a single female is 18, the pro* 
ductive period lasting from November 2 to December 1 (1909). Com¬ 
plete records on 20 individuals give an average of 8.4 eggs. The duration 
of the productive period is from 8 to 29 days. 
length of life of the sexes 
The majority of the oviparous females observed by the writer lived 
until killed by very low temperatures in November or December. The 
males do not live quite a month. The female just mentioned, that pro¬ 
duced 18 eggs, lived over a month after oviposition began, and was then 
killed by a severe freeze. Add to this her developmental period and she 
would be at least months old. This would probably be high for an 
average. 
molting 
Molting experiments have been conducted with each form and it 
was found that the stem mothers, winged and wingless forms, males, and 
oviparous females, without exception, molt four times. 
NATURAL ENEMIES 
APHIDIUS NIGRIPES 
The most efficient enemy of M. granarium is undoubtedly Aphidius 
nigripes Ashmead. As soon as A . nigripes becomes abundant,.the brown 
leather-like, almost circular bodies of the aphids will be noticed firmly 
attached to the plant. These contain the immature stage of the parasite. 
Just before harvest, if the infestation of M. granarium is heavy, the heads 
of grain will be almost covered with their brown, dead bodies. 
In the fall of 1908 sufficient data were secured to establish the parthe- 
nogenetic habits of this parasite. It produces only males under these 
conditions. 
On October 7, 1907, at Richmond, Ind., two virgin females were intro¬ 
duced into a cage with a number of M. granarium that had been grown in 
confinement and had not been parasitized previously. They began ovi¬ 
position at once. They would approach the aphid cautiously, bend the 
abdomen under until the tip extended beyond the head, then quickly 
stab the aphid. There does not seem to be any favorite point of attack, 
the parasite thrusting at the nearest point. The cage was kept out of 
doors in the rearing shelter and on November 1 the aphids began to 
