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10 15 20 25 30 35 40 45 
DAYS AFTER INITIAL MATING 
50 55 
70 
Fig. 7. Effect of ovariectomy on subsequent return of receptivity of 
females of N. cinerea. Open circles — ovariectomized only. Solid circles — 
ovariectomized ; glass tube inserted in uterus on the sixth or seventh days 
(arrows) after mating; tubes then removed 3-10 days after being inserted 
and the females kept with males until they mated. Numbers in circles 
indicate the number of females used. Per cent mating is expressed as 
accumulative data. 
the egg case blocked the bursa copulatrix. Thus in mated females, as 
in virgin females that oviposit (Roth, 1964), the mechanical 
presence of the odtheca inhibits receptivity. 
Ovariectomized (ovaries removed in last nymphal stage) females 
of N. cinerea mate within 3-6 days after emergence. When kept 
with males continuously only about 20% of ovariectomized females 
mated again and this occurred over about a 2-month period (fig. 7). 
Thus, either the lack of ovaries or ootheca in some way prevented 
return of receptivity. Sixteen pregnant females had their oothecae 
and ovaries removed 12-13 days after oviposition; eleven (69%) 
mated 7-17 days after the operation, showing that the presence of 
the ovaries themselves were not needed for the return of receptivity. 
N. cinerea nymphs were ovariectomized and the resulting adults 
were mated 3-6 days after emergence. After the spermatophores 
were dropped (6-7 days after copulation), glass tubes (about 4.3 
mm. X 10 mm.) were inserted into the uteri; the posterior ends 
of the tubes extended beyond the abdomen and were cemented to the 
last abdominal segment to prevent their being extruded. After re- 
