1964] 
Roth — Reproduction in Cockroaches 
237 
in ovariectomized females, and, if it controls receptivity it may 
explain our results with mated N. cinerea females whose ovaries 
were removed. Continued neurosecretory activity and the resulting 
high titer of hormone may tend to inhibit female receptivity for an 
abnormally long period. When oviposition is simulated by inserting 
glass tubes in the uteri of mated ovariectomized females and the 
inserts are removed after a few days, more females become receptive 
much more quickly than mated ovariectomized females that were 
not subjected to this treatment. Perhaps the insertion of the glass 
tubes resulted in stimuli that inhibited the neurosecretory system, thus 
preventing an increase in hormone titer. Upon removal of the 
artificial ootheca, the system is reactivated and the female mates. 
Thus, the results suggest that some center must first undergo a 
period of inactivity, induced by the ootheca in the uterus, for 
receptivity to return rapidly after parturition, or after removal of 
the egg case. 
The hypothesis that a low concentration of a hormone activates 
and a high titer inhibits a receptivity center could also explain 
why some females are unreceptive after parturition. These would 
be the individuals whose neuroendocrine systems become active in 
late gestation. Theoretically, these females should have become 
receptive in late gestation since they would have gone through a 
period when their hormone titer was sufficiently low to induce 
receptivity. That they do not mate in late gestation may be explained 
by the mechanical stimulation, resulting from the oothecae in the 
uteri, which suppresses mating behavior. That the same females 
do not mate even after parturition may be explained by assuming 
that the hormone titer has increased beyond the critical concentra- 
tion necessary to induce receptivity. A high hormone titer would 
also explain why females become unreceptive after being isolated 
from males for several days after parturition. Nutrition may act 
as a “trigger” stimulus to the neuroendocrine system, (de Wilde, 
1961). This could account for the prolongation of receptivity when 
females are starved during gestation and after parturition; presum- 
ably the absence of nutritional stimuli prevents the accumulation of 
neurosecretion and its consequent inhibition of receptivity. 
Females of D. punctata usually mate just after they emerge from 
the last nymphal skin, when they are still white and teneral. If iso- 
lated from males at emergence, the females tend not to mate (Stay 
and Roth, 1958). The mechanism governing this behavior is un- 
known. It cannot be correlated with increased activity of the corpora 
