1943] Bionomics of Ectopsocus pumilis 61 
also laid a group of eleven more eggs. These eggs were left out 
of doors and they hatched May 4. By May 12 these nymphs 
had reached the third instar. By May 25 they were in the sixth 
instar. The overwintering nymphs matured and deposited eggs 
that hatched, their nymphs likewise maturing. The overwinter- 
ing nymphs and adults, and the unsuccessful attempts to hatch 
overwintering eggs suggest that a few nymphs or adults manage 
to survive the winter and continue their normal activities in the 
spring. They were not found during late June and July, but on 
August 1 adults and eggs were taken on the dried leaves of new 
corn. 
Parasitism. — Groups of E. pumilis eggs were exposed to 
adults of Alaptus ccecilii Girault (Hym., Mymaridae) that had 
emerged from the eggs of Caecilius aurantiacus Hagen. Various 
groups of eggs were exposed on April 1, 5 and 11, but the eggs 
did not hatch and parasites did not emerge. The parasites were 
not definitely observed ovipositing in these eggs but they did 
walk over them. Other groups of eggs laid by the same female, 
not exposed to the parasites, hatched and matured normally. 
This scanty information suggests that A. coecilii oviposited in 
the eggs, that the embryo was destroyed and that conditions 
were not favorable for the complete development of the para- 
sites; so neither emerged. It is interesting to note that Spruyt 
(7) records Alaptus ccecilii from the eggs of Ectopsocus ccili- 
fornicus (Banks), the other species of this genus in the United 
States, and which is also parasitized by Alaptus psocidivorus 
Gahan. 
Summary. — Adults of Ectopsocus pumilis have been taken 
in many of the eastern states as far west as Missouri. Both 
sexes are known and the sex ratio is 0.5. The eggs are smooth- 
shelled and are laid in masses covered with a loose network of 
threads. The nymphs and adults feed on fungus, pollen, starch 
and embryos of the corn kernels and on the corn sheaths. The 
egg stage requires six days. The egg burster, apparently on the 
inside of the pronymphal membrane punctures the latter, while 
the chorion and vitelline membrane are probably broken by 
internal pressure. The nymphs swallow air bubbles at hatching 
and at moulting. The pronymphal membrane, with the egg 
burster attached, is always found protruding from the chorion 
after hatching. The antennae are eight-segmented in the first 
instar and thirteen-segmented thereafter. Wing pads appear on 
