62 



Insects and Disease 



fly feeds or while it rests and combs its body with 

 the rows of coarse hairs on its legs. 



The legs are rather thickly covered with coarse 

 hairs or bristles and with a mat of fine, short 

 hairs. On some of the segments the larger hairs 

 are arranged in rows and are used as a sort of 

 comb with which the fly combs the dirt from the 

 rest of its body. The last segment (Fig. 45) of 

 the leg bears at its tip a pair of large curved claws 

 and a pair of membranous pads known as the 

 pulvillae. On the under side of the pulvillae are 

 innumerable minute secreting hairs (Fig. 46) by 

 means of which the fly is able to walk on the wall 

 or ceiling or in any position on highly-polished 

 surfaces. 



HOW THEY CARRY BACTERIA 



These same little pads, with their covering of 

 secreting hairs, are perhaps the most dangerous 

 part of the insect for they cannot help but carry 

 much of the filth over or through which the fly 

 walks, and as this may be well stocked with germs 

 the danger is at once apparent. 



As the result of a series of carefully planned 

 experiments it has been demonstrated that the 

 number of bacteria on a single fly may range all 

 the way from 550 to 6,600,000 with an average for 

 the lot experimented with of about one and one- 



