ENTOMOLOGY

CHAPTER XXVThe Life History and Control of F1eas 1F. C. BiahoppThe importance of flea control probably needs no further emphasIsthan that already apparent after reading the lecture on the relationof fleas to disease. It should be borne in mind that the plague has beenone of the most terrible scourges in the history of the world and that itsreduction to an inconspicuous place in Europe and the western hemispherehas been the result of the knowledge of the relationship between rats andfleas and Bacillus pestis, the causative organism of the disease. Asidefrom the part which fieas play in the transmission of this dreaded maladyand certain other human ailments, they are often of decided importanceon account of the annoyance to man produced by their crawling aboutover the body and biting. The susceptibility to attack of individualsseems to vary greatly. In many cases a few fleas produce but littleannoyance and the bites leave no after effect. In other instances thecrawling of the fleas produces much annoyance and the bites have beenknown to form lesions of more or less serious character and often slowto heal.To proceed intelligentlir with flea control it is important to have agood general knowledge of their habits and distribution. Eleven speciesof fleas have been shown capable of carrying plague. Eight of thesehave been found to occur on one or more species of rat (Epimys spp.)and two on ground squirrels. Of these, the Indian rat fiea undoubtedlyplays the principal role in the transmission of bubonic plague. Thefollowing list includes most of the forms which may be ~onsideredimportant to man either as vectors of disease organisms or as annoyers:Pulex irritans, Ctenocephalus' canis, Ct. felis, CeratophyllUIJ fasciatus, C.aniaiu, C. acutus, X enopsyZZa cheopia, X. scopUlifer, CtenophtlwZrnusagyrtes, Dermatophilus penetram, Echidnophaga gallinaccus, Hoplopsyllusanomalus.The host relations of fleas are very important, as has been seen byconsidering the relationship of the insect to disease transmission. Unfortunatelymost of the fleas are not very closely restricted to certain hosts,especially when forced by hunger to seek blood., .• This lecture was read November 4, 1918.360It might be stated at