SOME NEW FACTS ON THE BIONOMICS OF THE 

 CALIFORNIA RODENT FLEAS. 



'SI. Bruin Mitzmain, B. S., 

 University of California. 



The thorough investigations which the United States Pubhc 

 Health and Marine-Hospital Service are at present undertaking 

 in suppressing bubonic plague in California presented the writer 

 with an opportunity to study the parasites associated with the 

 transmission of the disease among rodents. 



In this contribution we have not taken into account the fac- 

 tors involved in the epidemiology, but have restricted the scope 

 of the paper to a discussion of the general habits and transfor- 

 mations of the California rodent fleas. Many of the observations 

 on the bionomics of the fleas are quite different from those re- 

 corded by the investigators of the English Plague Commission in 

 India. This is due in a measure to difference in climatic condi- 

 tions, to which fleas as a rule are easily influenced; and the dift'er- 

 ence in the species of flea. The English workers confined their 

 experiments to one species, namely, the Loemopsylla chcopis 

 Roth. We have considered the rodent fleas generally, giving 

 most attention to the squirrel flea C. acutus Baker. 



FLEAS IN RELATION TO THEIR ENVIRONMENTS. 



We have made an effort to rear fleas in the laboratory by 

 attempting to duplicate conditions found to exist in nature. The 

 human flea, P. irritans Linn, was found to develop very satisfac- 

 torily in a medium composed of floor sweepings taken from the 

 cracks in the floor. The squirrel fleas and rat fleas were found to 

 develop well in material taken from the nests of their respective 

 hosts. We have experienced no difficulty in raising these para- 

 sites by placing animals covered with fleas in cages with a bed- 

 ding of sawdust; and the only provision necessary for complete 

 development was the addition of fresh sawdust to prevent the 

 accumulation of too much moisture. 



An experiment was made to determine in what media fleas 

 away from the host would survive longest. For this purpose 

 we tested various materials shown in the following table : 



6i 



