562 



Plague 



is common everywhere as is Pulex irritans, the human flea. It is likely that any 

 or all of these engage in plague transmission when once an epidemic has started, 

 but the most active vector of the disease, the world over, and the most important 

 agent in starting human epidemics of plague is Xenopsylla cheopis. 



Much interesting and valuable information concerning the biology, bionomics 



Fig. 233. Various fleas, magnified about 30 diameters. The specimens are 

 treated with hot 20 per cent, caustic potash for a few minutes, dehydrated in 

 alcohol, cleared in xylol and mounted in balsam, a, Pulex irritans, cf ; b, Pulex 

 irritans, 9 ;c, Xenopsylla cheopis, cf ; d, Xenopsylla cheopis, 9 (Bacot, in Journal of 

 Hygiene, "Plague Supplement in, 1914"). 



and relation of rats and fleas to plague, will be found in the " Reports of the India 

 Plague Commission " many of which are to be found in the "Journal of Hygiene," 

 vols. i-xiv. 



The following illustrations and tabulations will enable the student to identify 

 the common genera of fleas. For more intimate systematic study he must be 

 referred to "A Text-book of Medical Entomology," by Patton and Cragg.* 



* " Christian Literature Society of India, London, Madras and Calcutta," 1913. 



