Oct., '08] ENTOMOLOGICAL NEWS. 359 



presented when live tissue is not directly available. A bite 

 from the fly after such infection would indeed prove disastrous. 

 Careful observers have noted in the history of an outbreak- 

 in its incipiency that it becomes effective in this wise : First, 

 it is observed that an unusually large number of rats in a cer- 

 tain locality come out into the open and, acting queerly, un- 

 conscious of the presence of enemies, die in a short time. Then 

 ensues a lull of several days, followed by the illness of the first 

 human victims. It is during this lull in the history of a plague 

 epidemic that there appears to exist an abnormal supply of rat 

 fleas. This latter fact is amply illustrated from incidents in 

 the San Francisco epidemic. In the early part of the cam- 

 paign Dr. William Wherry, Bacteriologist of the San Fran- 

 cisco Health Department, collected one hundred and eighty 

 fleas from two rats sent in from the Latin Quarter, a pest- 

 ridden district. On four rats taken from Meigg's wharf in 

 San Francisco there were counted approximately two hundred 

 and forty fleas. Three of these rats were autopsied and one 

 was found to have a pronounced case of plague, verified by Dr. 

 Hobdy, U. S. A., clinically and bacteriologically. Under nor- 

 mal conditions and in districts removed from plague, the rats 

 harbor an average of three or four fleas. 



Observations were taken to determine whether rat fleas 

 will bite the human. Baker states (Proc. U. S. Nat. A'lus. '05) 

 that rat fleas in America were never known to bite man. Since 

 we know definitely how the plague is transmitted from rat to 

 man it must be taken for granted at the outset that man has 

 been rat flea bitten in many instances, as the San Francisco 

 official plague records will show. Specific instances can be 

 cited. In the improvised bacteriological laboratory of the San 

 Francisco Health Department hundreds of dead and live ro- 

 dents were brought daily. Fleas from these rats hopped freely 

 about the floors and work tables, making things irritable for 

 attendants and health officers. On shipboard nine specimens of 

 rat fleas were collected preying on one of the surgeons in the 

 United States Public Health Marine Hospital Service. My 

 personal experiences contribute the fact that rat fleas taken 

 directly from live rats or even rats which have been dead for 

 several hours, will not bite the human until they have been per- 

 mitted to starve in a test tube for two days or longer. 



