To learn the probable degree of infectibility of the port with bubonic plague, live rats (1561) were trapped, of which 1557 were Rattus norvegicus and 4 were R. rattus rattus. Of the 4,898 fleas taken, 3,999 (81.6%) were Xenopsylla cheopis; 864 (17.7%) Ceratophyllus fasciatus; 28 (0.6%) Ctenocephalus canis (or felis); 6 Leptopsylla musculi and 1 Echidnophaga gallinacea. The ave. number of fleas per rat was 3.14. The aye. number of X. cheopis per rat was 2.56; this species predominated from June, 1927, to Feb. 1928. The cheopis index followed fairly closely the seasonal variation curve of relative humidity and temp. Among parasites other than fleas, Polyplax spinulosa (Burmeister) was occasionally found, and a considerable number of mites 2,646 Laelaps echidninus (Berlese), 4 L. hawaii-ensis (Ewing), 20 Liponyssus bacoti (Hirst) and 1 Veigaia.