200 



IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



The Sixth Nymph. — A sixth nymphal stage usually occurs in 

 this species, but not always. One of the male individuals reached 

 maturity in the sixth stage. The length of tliis stage when it 

 does occur was determined for two individuals. One passed the 

 stage in 14 days, the other in 29 days. 



Number of Nymphal Instars. — Data were obtained in regard 

 to the number of molts and nymphal instars for seven different 

 individuals. Thev are here given : 



Number of 

 Individual 



Nr:MBER Nymphal 



In STABS 



Sex 



Notes 



Female] Mated with 2 males after 

 j4th molt. 



? Died after 8th molt. 



Male Showed characters of male in 

 last nymphal instar. 



Female Kept through season follow- 

 ing her maturity. Mated 

 ' and spun cocoons. ' No more 

 molts. 



Female Kept through season follow- 

 ing maturity. Did not molt 

 after becoming mature. 



Female Died at end of sea.son. 



Female Died at end of season. 



From these data it appears that the number of molti^ for each 

 individual varies considerably. In the ease of female!* it was 

 found to vary from four to eight. No data were obtained in 

 regard to the variation of the number of molts in the case of 

 the male. It was feared that this apparent variation in tbe num- 

 ber of nymphal instars was due to individuals molting after 

 reaching maturity. In regard to this point, though, it was 

 later shown that molting does not take place after reaching 

 maturity. Two of the individuals reared in one .season, were 

 kept through the next, and neither of them molted during the 

 second season. Again, observations of mature males and females 

 kept in captivity did not reveal molting after maturity was 

 reached. 



Lotigevity of Adults. — The house spider is probably uot long- 

 lived. Individuals which hatch out in the spring, if properly 

 fed, will reach maturity by the following winter. These over- 



