FLEAS. 7 



insect has become adult. Observations made in India and in our 

 own country in the vicinity of San Francisco show that there is no 

 complete cessation of activities in the winter. This is also true as 

 observed in several species by Mr. A. H. Jennings, of the Bureau of 

 Entomology, while in Panama, and the author has observed con- 

 siderable numbers of fleas on hosts in the Southern States in mid- 

 winter. These included the dog flea and the chicken flea, or " stick- 

 tight," as it is colloquially known. 



LIFE CYCLE. 



The total period from the deposition of the egg to the emergence 

 of the adult, in tests with the dog flea conducted during the summer 

 time at Washington, ranged from 17 to 35 days. The length of the 

 different stages and total life cycle of some of the common species of 

 fleas may be shown best by presenting a table compiled by Mitzmain 

 from the works of various authors, and amplified to include recently 

 published results. 



Table I. — Life cycle of fleas in different countries. 



Country and species of flea. 



Length of 

 egg stage. 



Length of 

 larval 



Length of 

 cocoon 



Length of 



complete 



cycle. 



United States: 



Atlantic coast- 

 Dog flea ( Ct. cams) 



Pacific coast- 

 Human flea (P. irritans) 



European rat flea ( C. fasciatus) 



Indian rat flea (X. cheopis) 



Ground squirrel flea ( C. acutus) 

 Europe: 



Human flea 



Log flea 



European rat flea 



Indian rat flea 



Bird flea ( C. gallinae) 



India: 



Indian rat flea 



Australia: 



Human flea 



Days. 

 2 to 4 



7 to 9 

 5 to 6 

 9 to 13 



7 to 8 



4 to 12 



8 to 14 



5 to 14 

 10 or less 



7 or less 



Days. 

 8 to 24 



28 to 32 



4 to 7 



32 to 34 



26 to 28 



8 to 100 

 12 to 142 



12 to 114 

 14 to 84 



13 to 50 



Days. 



5 to 7 



30 to 34 



24 to 26 



25 to 30 

 24 to 27 



6 to 220 

 10 to 354 



3 to 450 

 9 to 191 



6 to 70+ 



7 to 14 



Weeks. 

 2 to 4 



11 



11 



9 to 



7 to 

 9 to 



8 to 

 Days. 



19 to 264 

 35 to 366 



20 to 467 

 31 to 256 

 26 to 127 



21 to 22 

 Weeks. 



4 to 6 



LENGTH OF LIFE OF THE ADULT. 



Food is the most important single factor in longevity of the flea. 

 Comparatively cool, humid weather greatly lengthens life. Mod- 

 erately warm, moist weather is more favorable than cool weather for 

 egg laying, but shortens the total life period. Hot, dry weather soon 

 proves fatal to the adult. In connection with this subject reference 

 is made to the work of Mr. Bacot in England, as he has conducted the 

 most complete set of experiments yet published to determine adult 

 longevity. When the temperature registered from 45 to 50° F. and 

 the air was nearly saturated with moisture, this investigator found 

 that specimens of the human flea lived for 125 days, the European rat 



