211 



He therefore secured collecti<ms of rat-fleas in tlie Punjab, Madras 

 and Bombay Presidencies, Central India and Hurma. A total of 

 17,358 fleas was examined, the technique employed being described. 

 The results, given in tables, show that X. astia and X. cheopis are 

 both common fleas in those parts of India, 53-9 per cent, of those 

 examined being X. cheopis and 36 per cent. X. astia ; minor species 

 being X. brasiliensis (7 -1 per cent.), CeratophyUus (2-1 per cent.), 

 and Leptopsylla nmsculi (0-3 per cent.). The tables show that the 

 distribution of the three main species is very irregular, and, in the case 

 of X. astia and X. cheopis, is not clearly correlated with any of the 

 factors that ordinarily govern the geographical distribution of animals. 

 The case of A', brasiliensis is less obscure. 



India may be regarded as consisting, roughly, of Peninsular India 

 (the tableland of the Centre and South) and Extra-Peninsular 

 India (the Indo-Gangetic Plain extending from the coast to the foot 

 of the Himalayas on either side of the Peninsular and rising only a 

 few hundred feet above sea-level). The habitat of X. brasiliensis 

 is clearly Peninsular India, the characteristics of which are the absence 

 of extremes of temj^erature and moderate humidity. CeratophyUus 

 piinjabensis and A', brasiliensis were not found to occur together. 

 A', astia and A', cheopis occur equally in the Peninsular and Extra- 

 Peninsular portions, but it is evident that X. cheopis is the commoner 

 species in the Punjab, and A', astia on the Madras Coast ; in some 

 stations on the Peninsular A', astia seems to be replaced by X. brasi- 

 liensis ; all batches of fleas containing A', brasiliensis also contain 

 A. cheopis. A map, showing the means of temperature and humidity, 

 indicates the bearing of climate on the relative prevalence of the chief 

 species ; the Punjab stations with an annual mean temperature of 

 less than 77 • 5° F. show a high percentage of A', cheopis ; those with a 

 mean annual temperature of 77-5 to 79° F. show a higher proportion 

 of A. astia. Of 1,421 fleas sent from Akyab, however, only 2-2 per 

 cent, were A^. cheopis, while at Rangoon, not far distant and with 

 a similar climate, the numbers of this species and of A', astia were 

 equal ; this and other examples clearly show that it is not possible 

 to correlate the constitution of the flea population with climatic and 

 geographical conditions. Unfortunately the collections are insufficient 

 to allow of conclusions being drawn regarding seasonal prevalence 

 of the species ; indications are that A', cheopis rises to a higher 

 prevalence during low temperature and a high degree of humidity 

 than either A', astia or A', brasiliensis. 



An examination of the hosts from which the fleas were obtained 

 shows that either A. astia or X. cheopis may exist on any one of 

 several rodents, as would be expected. 



Of the other rat-fleas, eight species of CeratophyUus have been 

 recorded from rats and squirrels in India, of which C. fasciatus, 

 common on rats in Europe, is very rare. C. punjabensis was fairly 

 abundant throughout the Punjab, but disappeared during the hot 

 weather ; C. nilgiriensis occurred in numbers in Madras. The genus 

 was represented by only one individual in collections from Bombay. 

 L. muscidi was found only at Ootacamund. The absence of fleas 

 other than rat-fleas proved remarkable ; only ten individuals of Cteno- 

 cephalus felis (the common flea of dogs and cats in India) occurred, 

 and not a single Pulex. 



As regards the relation of rat-fleas to the epidemiology of plague, 

 the present observations are not sufhcicnt for conclusive results, but 



