6 STUDIES IN INSECT LIFE, ETC. 



The difficulty of keeping the male and female 

 alive was simple compared with the difficulty of 

 rearing the eggs. Very few hatched out. The 

 strands of cloth upon which they were laid had 

 been carefully removed and placed in separate 

 tubes, at the same time being subjected to differ- 

 ent temperatures. It was not, however, until 

 the eggs were left alone undisturbed in the position 

 where they had been laid and placed under the 

 same conditions that the mother lived in, that 

 eight and only eight, of the twenty-four eggs 

 laid on the cloth hatched out after an incubation 

 period of eight days. The remaining sixteen 

 eggs were apparently dead. But the tube in 

 which they were was then subjected to the normal 

 temperature of the room at night (on occasions 

 this fell below freezing-point), and after an incu- 

 bation period of upwards of a month six more 

 hatched out. Hence it is obvious that, as in the 

 case of many other insects, temperature plays a 

 large part in the rate of development, and it 

 becomes clear that the eggs or nits of P. vesti- 

 menti are capable of hatching out up to a period 

 of at least from thirty-five to forty days after 

 they are laid. 



Difficult as it was to keep the adults alive, and 



