62 
Psyche 
[June 
colony by Dr. Barbara Stay of our laboratory. Two of 
these were observed expanding- the end of the abdomen. 
Althoug-h the oothecae did not protrude beyond the ends 
of the abdomens, the distal ends of the oothecae could easily 
be seen in profile as the females separated their genital 
segments. The axes of the eggs were vertical at this time. 
These oothecae were rotated a short time later, cephalic 
ends of the eggs to the females’ left, and retracted into the 
brood sac. The females were then dissected; the oothecae 
contained 11 and 10 eggs, respectively. 
The fourth female was seen with the first egg and parts 
of the succeeding two eggs protruding beyond the end of 
her abdomen. The axes of the eggs were vertical, but with- 
in a few minutes the female rotated the ootheca, as above, 
and retracted it. This ootheca was later found to contain 
13 eggs and the female’s right ovary had seven and the 
left six ovarioles. These observations show that our a 
priori hypothesis of oothecal formation in Diploptera (Roth 
& Willis, 1954) is correct, being similar to that found in 
other cockroaches. 
Protrusion of eggs beyond the end of the abdomen dur- 
ing oothecal formation apparently depends on such factors 
as size and number of eggs and size of the female. From 
our observations, it seems likely that few eggs protrude 
beyond the female’s body and that protrusion occurs rather 
infrequently. 
Since writing the above we have seen oviposition several 
more times; ovipositing females were recognized when 
they repeatedly expanded and contracted their genital 
segments. The first laid egg was visible for only a short 
time from behind or from the side. Rotation and retrac- 
tion of the ootheca occurred rapidly, in a matter of minutes. 
Explanation of Plate 5 
Figures 5-13. Eggs of Diploptera dytiscoides (X5). Figs. 5-9. Eggs of 
various ages showing increase in size. Actual lengths of the eggs as 
follows: fig. 5. 1.7 mm. (note lack of visible differentiation; upper limit 
of thin oothecal membrane indicated by arrow); fig. 6. 3.1 mm.; fig. 7. 
4.3 mm.; fig. 8. 5.7 mm.; fig. 9. 6.9 mm. (arrow indicates a strand of 
greatly stretched, perforated oothecal membrane). Figs. 10-13. Sequence 
showing hatching of 2 eggs from ootheca shown in figure 9; hatching 
occurred within 3-minute period. 
