206 Psyche [December 
Fig. 6. Effect of reducing the number of eggs in the ootheca on the size 
of oocytes at parturition in N. cinerea. Open circles — number of eggs in 
oothecae reduced manually (N = 66). Solid circles — number of eggs in 
oothecae not reduced manually (controls; N = 84). Each circle represents 
one female. Arrows indicate the average number of eggs in the oothecae 
for the 2 groups of females. Numbers in brackets are the mean lengths ± 
standard errors of the oocytes for both groups. Oocytes were measured 
<24 hr. after parturition. Gestation period for the females whose oothecae 
were artificially reduced in size averaged 60 days and for the control group 
58 days. (Room temperature.) 
very few eggs, are important in inhibiting the corpora allata during 
pregnancy. 
Mechanism of inhibition of receptivity during gestation 
Pregnant females of N. cinerea are unreceptive and do not respond 
to the courting male (Roth, 1962). Eight pregnant females had 
their ventral nerve cords transected <24 hr. after ovipositing. They 
were exposed to males for 1-2 hr. trials daily to determine if they 
would mate. Six females mated in 2 - 8 days after cord transection ; 
one mated 18 days after transection. The spermatophores were 
attached to the surface of the ootheca, usually in the vestibule, because 
