Séance du 16 Avril 1924 
145 
on two successive days or with an interval of one day 
between the main emergences. 
Very few 7 young fail to liberate themselves from 
the hatching sheath when emerging from fertilized 
egg-cases. On the contrary an average of over io % 
fail to do so from unfertilized egg-cases and the num¬ 
ber may reach 20 % of the total. 
8. Even at the most favourable time of the year, 
the incubation period is tw o or three days longer for 
egg-cases laid by virgins than for those laid by fer¬ 
tilized females. 
9. Not only do many of the young fail to free 
themselves from the hatching sheath, but a large 
number die before the first moult — of those we tried 
to bring up as many as 5 o % — and more than half 
of the remainder failed to reach the last moult. 
Less than 2 % of those which hatched from fer¬ 
tilized egg-cases failed to free themselves from the 
hatching sheath or died before the first moult and 
over 60 % of those we tried to bring up reached the 
adult stage in spite of the fact that many w 7 ere given 
as prey to their older relatives in times of scarcity of 
food. 
10. All the adults obtained from unfertilized egg- 
cases were females, the immature stages were not 
examined owing to the difficulty of distinguishing the 
sexes at an early stage in this species. 
From fertilized egg-cases approximately equal 
numbers of both sexes were obtained, the females 
