968 SANITARY ENTOMOLOGY 



be taken against flea bites. Workers should be provided with closely- 

 fitting clothes and leggings and certain other methods of body isolation 

 as discussed in a subsequent paragraph. 



When operating in regions where plague is suspected, it is also im- 

 portant to choose locations for troops which are apt to be free from 

 rats. The billeting of men in old buildings, warehouses, barns, etc., should 

 under such conditions be entirely avoided. 



Control of Hosts. — To keep down heavy infestations of those species 

 of fleas which are annoying to men and animals, one of the essential steps 

 is to exercise control over the hosts. Of course, this principle is involved 

 in the elimination of rats and squirrels in plague areas. When an infes- 

 tation is encountered, the first thing that should be inquired into is the 

 possible hosts and their haunts. Usually the main trouble can be traced 

 to the sleeping places of dogs, cats, hogs, or to hen houses, or spaces 

 beneath houses and bams frequented by poultry. In the case of the 

 human flea the infestation may be more or less general over the premises, 

 but there are nearly always centers where they are concentrated and 

 often these are associated with pet animals. When the principal breeding 

 places have been located the hosts should be destroyed if possible, or 

 freed from adult fleas, and kept under control. A definite sleeping 

 place should always be provided for dogs and cats, and these may be 

 kept free from fleas, after treatment, by cleaning out the beds regularly 

 and spraying with coal tar disinfectant. The host animals may be freed 

 of fleas by washing them thoroughly in a S per cent solution of creolin 

 and water, or by using any other standard saponified creosote compound. 

 Kerosene emulsion made according to the formula : One pound soap, two 

 gallons kerosene, one gallon water, reduced one to nine, is also very effec- 

 tive. In the case of cats these substances must be washed out of the fur 

 with warm water and soap shortly after treatment to avoid burning of 

 the skin.^ 



Where premises are heavily infested with adults it is first necessary to 

 destroy this stage and this may be accomplished by fumigation, if the 

 building is fairly tight, either with hydrocyanic gas, five ounces cyanide 

 per thousand cubic feet ; or by burning sulphur at the rate of four pounds 

 per thousand cubic feet. As has been pointed out, many adults remain 

 quiet in pupa cases or may be buried in sand or cracks where they are 

 somewhat protected from the efi^ects of the gas. In destroying the imma- 

 ture stages we can take advantage of the destructive effect of extremes in 

 moisture or dryness. Where complete flooding of infested areas is feasible, 

 this has been known to accomplish the destruction of all stages. In other 

 cases, loose boards and trash should be removed and burned and the 



' Powdered derris has been found very efficacious in destroying fleas on animals. 

 One grain scattered in the hair of a dog will kill all fleas present. 



