THE HOUSE SPIDER . 195 



The number of eg'gs laid in a single cocooii varies greatly, aiid 

 since th:^re is a great variation in the number of cocoons spun 

 by a single female there will be a great variation in the total 

 number of eggs laid by her. Tlie egg laying record of one female 

 is here given : 



According to these records the average number of eggs laid 

 in the cocoon is 65 -|-, but the writer is of the opinion that this 

 is considerably less than the average that would have been ob- 

 tained if many counts had been made. Likewise the total of 

 261 eggs for a single female is probably low. This particular 

 female was fertilized only once during her life — before the first 

 egg mass was deposited. If she had been fertilized before each 

 oviposition it is probable that the number of eggs would have 

 been greater. This point has not been ascertained, however. A 

 sino^le count made of the eggs in a cocoon of another female gave 

 213. That the number of eggs laid in a single cocoon may even 

 exceed thi.s latter number is clearly shown in the counts of the 

 spiderlings emerging from a single cocoon. One of these counts 

 gave no less than 254 spiderlings coming from a single cocoon. 



First, or Quiescent Nymph. — There is one thing in the life 

 history of this spider, as well as others, that is very unusual in 

 arthropods and its significance from the standpoint of racial 

 advantage is hard to understand. The reference is to the occur- 

 reiice immediately following the egg of a quiescent instar. In 

 the case of insects with a complete metamorphosis, there is a 

 quiescent instar, but it follows the feeding, growing instar, the 

 lar\^a, and its advantage is clearly evident. The larval or 

 caterpillar stage, which is a later development in the phylogeny 

 of insects, is an adaptation which permits the individual to feed 

 voraciously for a short time, make its growth, and store up 

 energy in the form of fat. Now it can seek a hidden protected 

 place, -where it would be probably impossible to obtain food, but 

 w'here it is concealed from most of its enemies, and here it slowly 

 transforms into the adult. The occurrence of the pupal stage 

 in insects follows the development of a specialized larval stage. 



