BIOLOGY 



Life Cycle 



Laboratory studies indicate that R. s. simus undergoes a three- 

 host type of life cycle. "" 



Under experimental conditions, Theiler (unpublished), Lewis 

 (1932A) , and Loionsbury (19O5) have found the life cycle periods 

 to be as follows: 



PERIOD 



DAYS 



OC. TEMPHIA.TURE 



Theiler Lewis Lounsbury Lewis 



80.125 111 



Note: Theiler rearings at 24°C. to 26°C. and approximately 8C5S R.H. 



Hares were used as hosts for all stages in Lewis* experiments, 

 though not with great success. The ease with which these observa- 

 tions could be repeated using normal hosts and normal conditions 

 of temperatiore and humidity found in rodent bijrrows suggests an 

 interesting study for collecting comparative data. 



Field observations indicate that both immature stages feed 

 on nest- inhabiting rodents. The nymphal-adult molt occurs in 

 the same nest, and adults remain in the nest for some time before 

 seeking larger hosts. As discussed below, a considerable amount 



*2 months in winter. 



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