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[December 
(table 2). These results again show that after parturition, recep- 
tivity can be correlated with relatively small oocytes because females 
with longer gestation periods usually have large oocytes at parturition. 
It appears that if the oocytes begin to mature several days before 
the female gives birth, she will tend to be sexually unreceptive after 
parturition. 
If large oocytes are an indicator of nonreceptivity following partu- 
rition, then females that are receptive at parturition should become 
unreceptive if isolated from males for several days after giving birth 
because an additional mating is not necessary for continued develop- 
ment of the oocytes. The effect on receptivity of isolating females 
from males for various periods of time after parturition and then 
placing them with males until they mated or oviposited is shown 
in figure 10. There was a marked decline in receptivity of females 
after they had given birth, the longer they were isolated from males. 
The oocytes of 30 females that mated after being placed with males 
2-6 days after parturition averaged only 1.40 d= 0.06 mm., indi- 
cating that in these females the oocytes were relatively small at 
parturition. The largest oocytes of all the females that mated follow- 
ing a delay in exposure to males was 2.21 mm. (she mated 6 days 
after parturition). 
Females of L. maderae usually mate within a day or two after 
parturition and mating after parturition is not required to mature the 
oocytes. As in N. cinerea, delayed exposure to males also results in a 
loss of receptivity in fed females (table 3). 
Return of receptivity of females after removing the oothecae from 
the uteri 
Roth (1962) found that the elapsed time for the return of 
receptivity following removal of the oothecae was shorter when the 
egg case was removed late rather than early in gestation; in that 
experiment the actual ages of the oothecae when removed from the 
uteri were unknown. The return of receptivity in females which 
had their oothecae removed at several known periods following 
oviposition is shown in table 4 and figures 11 and 12 (done under 
different temperature conditions). More than 50% of the control 
females became receptive within a few hours after giving birth (fig. 
11, AP). The time required for the return of receptivity in the 
experimental animals varied and depended on how long the females 
had been pregnant when their oothecae were removed. The younger 
the oothecae when removed, the longer it took for the return of 
