THE LIFE OF THE SPIDER 51 



generation per year, while in the colder northern reaches some of 

 the species probably require two or more years to attain complete 

 maturity. 



The life of the male is invariably shorter than that of the female. 

 Males of the spring spiders die in early summer after having lived 

 about ten months. The same longevity holds true of the fall species, 

 and the females outlive the males by several weeks. Under laboratory 

 conditions, G. and E. Deevey found that average male black widows 

 matured in about 70 days and lived a total of about 100 days; 

 whereas females matured in 90 days and lived about 271 days. The 

 greatest life span for the males was 160 days, and for the females 

 550 days. Such data show that mating between brothers and sisters 

 of the egg masses is quite improbable. 



A number of spiders are known to live more than one year. 

 In the northern United States almost the only ones to do so are the 

 large wolf spiders, which burrow into the soil and probably live 

 several years. Occasionally other spiders live about 1 8 months, such 

 as the large water spiders and the black widows, even though their 

 normal life span is only a year. 



The more primitive true spiders often live more than a single 

 year. Some of the segestriids and scytodids are said to be peren- 

 nials, and Dr. Lucien Berland kept a female filistatid for ten years. 

 It is probable that all ancestral spiders were longer-lived, and that 

 one of the sacrifices of the modern true spider for the many advan- 

 tages it enjoys is a drastic reduction in life span. 



It is generally believed that all mygalomorph spiders live several 

 years. The purse-web spiders are reported to live as much as seven 

 years, and the true trap-door spiders are also perennials. Exceeding 

 all other spiders in length of life are the large tarantulas. Dr. Baerg 

 has kept a female tarantula for more than 20 years and believes that 

 25 or even 30 years probably represents the normal age for females. 

 The males mature in 8 or 9 years, but ordinarily die a few months 

 afterward. 



