82 Annals Entomological Society of America [Vol. Ill, 



average length of the stages of development, in C. acntiis as a 

 type, are as follows: 



Egg stage 8 days 



Larval stage 28 days 



Cocoon 31 days 



Adult without host 32 days and longer 



13. Fleas which have never been fed from the time <jf 

 emergence from the cocoon prove longer lived when starved than 

 fleas removed from the host. 



14. Rat fleas may be kept alive on a human host for a 

 considerable time, one specimen being kept alive as long as five 

 months. 



1 5 . The females of all species of fleas are considerably longer 

 lived than the males. 



16. Induced parasitism of rodent fleas on man seems to be 

 influenced by the length of mouth parts in the different species. 

 One specimen of C. acntus, the species with the longest rostrum, 

 fed for a period of nearly one hour at one insertion of the mouth. 



17. It is indicated that starvation of infected fleas, when 

 these insects are transported in clothing, may not eliminate the 

 danger of transmission of plague. 



