34 NEW YORK STATE MUSEUM 



life cycle of 5 to 6 weeks. The human flea develops somewhat 

 more rapidly, the egg stage being given as from 4 to 6 days, the 

 larval period u days, and the duration of the pupal stage 12 days, 

 making a generation possible in 4 to 6 weeks. The Indian rat flea 75 

 has an egg period in India of 2 days, though in California, accord- 

 ing to Mitzmain, 76 it may vary from 9 to 13 days, while the usual 

 larval existence, 8 to 24 days as given by American and English 

 authorities, is extended in California under laboratory conditions 

 to rarely less than 28 and even 30 days, and sometimes longer. The 

 adults of this species may live on rats in India for 41 days, the 



Fig. 12 Cat and dog flea, seen from the side, enlarged. (Author's illustration) 



maximum on an exclusive diet of human blood for that locality 

 being 27 days, though in California the species may be kept alive 

 under such conditions for 36 days. Fleas may live in bran in the 

 absence of liquid food for 6 days, and in sand with moist cow 

 dung for 13 days. 



Sandy soil is most suitable for flea development, and undis- 

 turbed dry dust in buildings and sheds appears particularly favor- 

 able. The custom of setting buildings on foundations some dis- 

 tance from the ground, prevalent in the South, thus giving oppor- 

 tunity for cats, dogs and other animals to range beneath over a 

 usually dry soil, affords almost ideal conditions for the develop- 

 ment of these pests, and sometimes results in a general infestation 

 of adjacent lawns. 



75 X e n o p s y 1 1 a cheopis Roth. 



76 Pub. Health Bui. 38. 1910. 



