Oct., '08] ENTOMOLOGICAL NEWS. 353 



Insect Transmission of Bubonic Plague : a Study of 



the San Francisco Epidemic. 



BY M. B. MITZMAIN, B.S. 



The role of the flea in the transmission of bubonic plague 

 lends particular interest to observations on the species of fleas 

 infesting rats in the San Francisco epidemic. 



In the present campaign of rodent extermination eighteen 

 hundred rats have been examined by the writer. From the lat- 

 ter part of August to December ist he spent much of his time 

 in the plague-infected districts of San Francisco and other 

 towns where the existence of the plague was suspected. In 

 this connection an effort was made to locate the source of the 

 rat and flea introduction into the infected regions. 



SOURCE AND DISTRIBUTION OF SPECIES OF FLEAS. 



From coasting ships and river steamers the common flea ob- 

 tained was of the species Ceratophyllns fasciatus Bosc, and 

 those collected from ships from oriental ports were of the 

 species Ctenopsylla musculi Duges and Pule.r cheopis Roth. 

 There appeared to be a definite invasion of the introduced spe- 

 cies. Along the water front and east to the Latin quarter in 

 San Francisco there came to my obseravtion certain evidence 

 of flea introduction. As far as could be determined the orien- 

 tal rat flea seemed to disappear east of this line within ten city 

 blocks, and only the common rat flea, Ceratophyllus fasciatus. 

 made its appearance. In outlying districts I have not succeeded 

 in collecting ship rat fleas. I have secured negative evidence 

 to determine that the foreign fleas are alone responsible for 

 plague transmission. On twenty plague rats not one of the 

 alien species was obtained. The flea in evidence was that com- 

 mon to the Pacific coast, Ceratophyllns fasciatus. This spec ir- 

 is the predominant rat flea in the counties bordering the bay. 

 It was collected in San Francisco, Oakland, Point Richmond, 

 and in districts where plague had been reported by the local 

 health boards. At Point Richmond nineteen rat fleas were col- 

 lected in a warehouse which was a probable source of human 

 plague, and all proved to be the common species. From one in- 



