1962] 
Roth and Stay — Cockroaches 
191 
2.86 to 6.12 mm. (x=4.6odb0.23 mm.). One mated female that 
aborted an ootheca with undeveloped eggs after carrying for 79 days 
had oocytes 3.72 mm. long. It is apparent that toward the end of the 
“gestation” period in virgin females or once the time at which parturi- 
tion should normally take place is passed, the inhibition of the corpora 
allata (due to the presence of the ootheca in the uterus) breaks down 
and these endocrines again secrete the gonadotropic hormone. Eleven 
virgin females that aborted their oothecae 91 to 104 days after ovi- 
positing, were kept until they ovulated a second time. Five of the 
females oviposited in 21 to 30 days (x=25.6d= 1.6) which is the 
same as mated females indicating that their oocytes at the time of 
aborting were relatively undeveloped. The other 6 virgin females 
ovulated in 11 to 18 days (x= 14.8=!= 1 .4) undoubtedly because their 
oocytes were already well developed when the egg cases containing 
undeveloped eggs were extruded from the uterus. 
Blaberus craniifer: The oocytes of this species at emergence are 
about 1.39 to 1.44 mm. (N = 2) in length. The mature oocytes are 
about 6.12 to 6.37 mm. (N=3) and at oviposition the new basal 
oocytes vary from 1.02 to 1.16 mm. (x= 1.09 ±0.03 ; N = 7). At 
parturition the oocytes are 1.34 to 1.85 mm. (x= i. 56±0.07 ; N = 
6). Gestation lasts 73 to 87 days (£=79.2 ±2.4; N = 5). After 
birth, a second ovulation occurs in 16 to 27 days (x=22.odz 1.9 ; 
N = 5) \ 
Six virgin females had their oothecae removed on the day of ovi- 
position. One oviposited again 47 days later. The others were dis- 
sected 44 to 60 days later and all had well-developed oocytes (3.96=11 
0.43 mm.). One female whose ootheca was removed 8 days after 
ovulation had oocytes 5.88 mm. long, 54 days later. Two females 
whose oothecae were removed 73 days after oviposition (i.e. close to 
parturition in mated females) had oocytes 3.23 mm. and 3.82 mm. 
long, only 10 days later. Removal of the ootheca in B. craniifer results 
in renewed development of the oocytes. 
The principal evidence for Engelmann’s (1957) hypothesis that a 
hormonal factor from uterine eggs inhibits the corpora allata via the 
brain was his claim that implantation of uterine eggs into the abdo- 
men of females of Leucophaea inhibited oocyte development, and 
nerve cord severance of pregnant females only had a slight but tem- 
porary effect on growth of the oocytes. However, more recently, 
Engelmann (i960) found that severance of the nerve cord in preg- 
nant females results in growth of the oocytes indicating that nervous 
stimuli may also be responsible for inhibition of the corpora allata 
during pregnancy. 
