ENTOMOLOGY

DISEASES CARRIED BY FLEAS 357in four per cent of rat fleas, Ceratophyllus fasciatus, and succeeded in infectingrats by feeding them on fleas. Johnston in Australia has corroboratedthe fact that this flea is a host, while Joyeux has proven that infectiontakes place easily in the larval stage, but is impossible in the adultflea. Johnston has found XenopsyUa cheopis to be a host. Joyeux hasinfected larvae of Pulex irritans and Ct(!'TU)cephalus coois. He found thatthe embryo develops independently of the metamorphosis of its host.The rodents become infected by licking up infected insects.Hymenolepis nana (Von Siebold), the dwarf tapeworm of rats andman, may possibly pass its intermediate stage in fleas. Nicoll and Minchinfound a cysticercoid in Ceratophyllus fasciatus resembling thisspecies, and Johnston in Australia also found a similar cysticercoid inXenops1JUa cheopis.Nemathelminthes: Nematoda: SpiruridaeProtospirura muris (Gmelin), a STOMACH PARASITE of rats andmice, has a larva similar to one found by Johnston encapsuled in thegeneral cavity of the rat flea, Xenopsylla cheopis.Nemathelminthes: Nematoda: HiZonUlaeActllnthocheilcmema recond.tum (Grassi), a cause of CANINE FIL­ARIASIS, possibly passes its embryonic development in fleas. Grassi andCalandruccio found larval nematodes in fleas, Ctenocephalus canis, C. felis,and Pule:c irritans that they assumed belonged to the species A. relJPnditum.The embryos, according to Grassi, perforate the intestinal wallof the flea which has ingested blood containing the parasites. The lattermake their way into the fatty tissue where they are almost always to befound lying singly in the fat cells. The fat cells increase in size as theparasites grow, the latter being curled up once or twice within the cell,the nucleus of which remains uninjured. The embryo undergoes fourstages of development in the flea. 'rhere is no positive proof of the methodof transmission.SUll4MARYIn summary, therefore, we may call attention especially to the factthat the flea carries plague, is apparently the carrier of infantile kalaazar, and is an intermediate host of one- of the human tapeworms. Inaddition it is intermediate host of various animal diseases.Unlike the louse-borne diseases, the life cycles of the organilrtns causingflea-borne diseases are quite variable.The bacilli of plague and rodent plague are taken up by the bite