Oct., '08] ENTOMOLOGICAL NEWS. 355 



plague have been removed from shipboard since the present 

 San Francisco epidemic. 



Ctenocephalus canis Curtis on rats appears to be more nu- 

 merous in the metropolis than on rats collected in the trans 

 bay region. This species was perhaps contributed to the rat 

 by its feline and canine hunters. This accounts probably for 

 the greater number of Ctenocephalus canis found on rats in the 

 more densely populated, quarters. On shipboard Ctenocephal- 

 us canis was never collected from rodent hosts. The ship cat 

 is not reputed to be a rat hunter. The constant petting and 

 feeding by the sailors does not stimulate hunting natural prey 

 and the inaccessibility of holds of vessels is a substantial check 

 to rat catching. Thus an interchange of parasites between 

 the two animals was not to be expected nor in any instance has 

 it been known to occur. Numerous ship pets inadvertently left 

 in the cabins during fumigation proved victims to the sulfur 

 fumes. One species of flea only, the cat flea, was found on 

 these. 



Relatively few fleas of the human species Pulex irritans Linn, 

 were obtained from live or dead rats. It was the least numerous 

 of all the fleas found on animal hosts. Those collected were 

 harbored by brown rats in a grain warehouse and stable in 

 San Francisco. 



In the study of ship rat fleas twenty-five vessels were in- 

 spected and methods of rat extermination investigated. The 

 vessels in every instance were thoroughly sealed and fumigated 

 with three per cent. SO2 gas obtained from burning crude sul- 

 fur. The rats when exposed to five hours of sulfuring are 

 blinded after the third hour, when they scamper about to escape 

 the deadly fumes before they succumb. Invariably the dead 

 rats are found with opaque lenses, an evidence of blindness 

 before death. Formerly three hours was the length of expos- 

 ure to sulfur fumigation. The rats were rarely killed, but mere- 

 ly rendered stupid by the fumes and men with clubs killed 

 them. Upon collecting these rats I found that the fleas soon 

 revived and gave evidence of their activity when the contain- 

 ers were opened. It was concluded that three hours' exposure 



