INSECTS AND DISEASE 377 



the floors, and in the sleeping places of cats and dogs, all these 

 places must be thoroughly cleaned when a house becomes 

 infested with fleas. Fleas are less apt to be troublesome in 

 houses where rugs are used instead of carpets, as the rugs are 

 more often taken outside for dusting and the floors more 

 thoroughly cleaned. Mats that can be easily cleaned should 

 be provided for the sleeping places of dogs and cats, and these 

 animals should of course be kept out of doors. Benzine, 

 naphthaline, pyrethrum and other substances are sometimes 

 used against fleas, but the results are not wholly satisfactory. 

 It is possible to kill all of the insects in the house by fumigation, 

 but fumigating is dangerous unless done by an experienced 

 person. 



House-flies. Until a few years ago the house-fly was looked 

 on as a harmless, although somewhat troublesome, household 

 pest, and was even regarded with some favor as it was sup- 

 posed that it was of service as a scavenger. But careful studies 

 of the insect and its habits have taught us to regard it in quite 

 a different light, and it is now regarded as one of the most 

 dangerous insects. It is hard to conceive of a better carrier of 

 small particles of filth and germs, or one with better opportuni- 

 ties for collecting and distributing them. Almost every part 

 of its body, and almost all of its habits, particularly adapt it 

 for the picking up and distribution of filth and germs. The 

 whole body is provided with a covering of spines and short soft 

 hair in which particles of dirt are easily carried. The blunt 

 end of the proboscis by which the fly sucks up its liquid food is 

 provided with numerous ridges and depressions so that some of 

 the material on which the fly is feeding is carried from one arti- 

 cle of food to another. The legs are particularly hairy, and the 

 last segment of each of the feet is furnished w r ith two little 

 pads which are covered with innumerable closely-set hairs that 

 secrete a sticky substance. It is the presence of these hairs on 

 its feet that enables the fly to walk on smooth perpendicular 

 surfaces, such as the windowpane, or on the ceiling, and, inci- 

 dentally, to carry along samples of the filth through which or 

 over which it walks. 



Ninety-eight per cent, of the house-flies lay their eggs in horse 



