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THE AUSTRALIAN MUSP:UM MAGAZINE. 



the European Hat Flea (C'erat(iphi/llu>> 

 fasciatus), the former bein<j by far the 

 more important. In Sydney tliree species 

 of fleas occur, commonly on rats— 

 Xennps//lla ch/o'pis, Cerutoplii/llus fas- 

 ciatus and Ctenopsylla musculi ; the lat- 



Mouse Flea (Ctenopsylla musculi). 

 Plioto. — K. Ciiant. 



their cocoon before emerging. As a rule, 

 liowever, the life cycle is completed in 

 under four Aveeks. 



The adult life under favoiu'able cir- 

 cumstances is a long one. Bacot founa 

 that the human flea (P. irritans) wa* 

 capable of living to 125 days without 

 feeding, but kept under cool, moist con- 

 ditions. Under similar eircumstanccM 

 the European rat flea (C. fasciatus) 

 lived 95 days, the dog flea (Ctenocep- 

 halus canis) 58 days and the Indian rat 

 •flea (X. cheapis) 38 days. This period 

 was greatly increased when the flea> 

 were fed daily, the maximum life being 

 for the various species as follows : — 



Human flea 513 days. 



European rat flea . ■ 106 days. 



Dog flea 234 days. 



Indian i-at (lea . . . 100 days, 

 ("onditions of moisture and coolness 

 are, however, indispensable, as in hot 



tor is the mouse flea, Imt is equally com- 

 mon on rats. 



In our knowledge of the bionomics ot 

 fleas we are principally indebted to the 

 Indian Flagaie Commission and to the 

 woi-k of Mr. Bacot of the Lister In- 

 stitute. 



All fleas ai'e dependeiil ii|)on blood for 

 theij- existence; most are connected with 

 some particular host, but there is con- 

 sideralde variation in the degree of re- 

 strict inn to their host, and in the absence 

 III' flic special host many species will 

 undoul)tedly attack other niiinials. in- 

 cluding man. 



Fleas pass thi-ough Four distinct stages 

 — egg, larva, pupa and adult. The egg> 

 are deposited by the female while still 

 on the host, and roll off mostly into the 

 bedding matei'ial, where they hatch in 

 two to twelve days. The lai'vae are 

 white, legless, segmented maggots, and 

 live in the dust of floors, crevices, or 

 in tlie open, sandy localities being pre- 

 fen-eil. The larval stage varies in dur- 

 ation according to circumstances, last- 

 ing under favourat)le conditions from 

 one to three weeks. When full grown the 

 larva spins its cocoon, in which pupa- 

 tion takes place. The pupal existence 

 \ai'ies tremendously, and fully formed 

 fleas may remain for long periods in 



Dog Flea (Ctenocephalus canis). 

 Photo.- — K. Grant. 



weather the duration of life without food 

 is but a few days. 



The question of how the flea conveys 

 infection to man has been the subject 

 of a large amount of investigation. The 

 Indian Plague Commission came to the 

 conclusion that infection took place 

 through the rubbing into the wound ot 

 the infected faeces of the flea. Bacot 

 and Martin showed that infection 

 could also take place directly into the 

 wound. These authors showed that the 

 proventricular valve at the entrance to 

 the flea's stomach ])ecame blocked by a 

 clot containing millions of the plagTit- 

 germs, and that after a time the clot 

 softened in the centre and, while inter- 



