1943] Bionomics of Ectopsocus pumilis 57 
Egg Stage. — Eggs (Fig. 1) are oval and flattened only on 
the surface contacting another object. The shells are smooth 
and shiny. Measurements of fifteen eggs chosen at random 
averaged 0.388 mm. in length and 0.208 mm. in width. The 
eggs were white when first laid, but turned a creamy yellow as 
development progressed. This change in color made the eggs still 
more difficult to find because they blended with the dried 
sheaths. They are easily overlooked because the silk is not 
dense enough to shine as it does in E. calif ornicus or C. manteri. 
Embryonic development was easy to observe in this species. 
The chorion and vitelline membrane remained practically trans- 
parent so the eyes of the embryo could be seen clearly on the 
fifth day of development, which was the day before hatching. 
Fifteen egg masses kept under laboratory conditions hatched on 
the sixth day. As the time for hatching approaches, the eggs 
become a little darker and the chorion wrinkles to the form of 
the body and appendages (Fig. 2). The embryo is ventral side 
up and the head, eyes, antennae, legs and tip of the abdomen 
are easily visible. The arms of the egg burster (Fig. 4) stretch 
across the front of the head with the center puncturing shaft 
projecting posteriorly toward the clypeus. The heads of several 
individuals were observed pulsating before the chorions were 
broken, and in one case as much as eight hours before. This 
activity, spasmodic at first, occurs at more regular intervals 
until at the time the chorion splits the top of the head is pulsat- 
ing regularly. Air bubbles appeared to be passing into the em- 
bryo through the mouth before the split in the chorion could be 
seen on the anterior end of the egg. 
Hatching. — The pronymph, within its membrane, slipped 
from the chorion and vitelline membrane with no apparent effort 
at first, then as it rose it swayed back and forth. Fifteen min- 
utes after the chorion was noticeably broken the egg burster 
punctured the pronymphal membrane. This differs from the 
report of Wachter (8) who states that the egg burster ruptures 
the chorion and that the vitelline membrane is broken by inter- 
nal pressure. This puncture lengthened to a slit that continued 
to progress toward the eyes. It required another fifteen min- 
utes before the head was completely free of the pronymphal 
membrane. At this time bubbles of air were passing into the 
head, which was becoming transparent. Thirty-five minutes 
from the time hatching started the head, thorax and most of the 
abdomen were out of the shell, and two minutes later the anten- 
