236 



Marvels of the Universe 



THE HOUSE FLY 



BY E. J. SPITTA, F.R.M.S. 



Considerable attention has 

 of late been directed to the 

 possibihty, if not the proba- 

 bility, that this household pest 

 can be a most dangerous 

 means of carrying infection. 



Before going further, it 

 should be at once mentioned, 

 that, although we have spoken 

 of the House Fly, as if one 

 type only existed, there are at 

 least four different kinds that 

 are popularly regarded as the 

 same. Of these, three are very 

 similar, only differing for the 

 most part in size and slight 

 modifications in the wing ; such 

 differences being only under- 

 stood and appreciated by the 

 expert. Each of them has a 

 suctorial mouth, too, that is to 

 say, has a tubular tongue for 

 obtaining its food, whereas 

 the fourth and largest variety 

 of all, the Stable Fly, is of 



The accompanying article and photographs will help to supply the deficiency. QuitC a different COnStrUCtlOn 



— at least, so far as its head is concerned; being provided with an apparatus for biting as well 

 as for sucking. This consists of lancets and a tongue. The first thing, then, to be kept in 

 mind is that the House Fly mostly met with does not bite, because it cannot, and that it is only 

 the much rarer Stable Fh' which is provided with instruments of torture. This statement, it should 

 be mentioned, is not common knowledge, nor, indeed, very possibly, is it in agreement with the 

 opinion of many, who, on the contrary, very confidently assert that House Flies do bite, especially 

 towards the end of the season. But it is in this last sentence that the controversv is explained. The 

 Stable Fly only puts in an appearance in houses towards the end of the summer, and its visits 

 last for a short period in comparison with those of the House Fly : hence, as this Stable Fly 

 can, and does, bite, and is usually mistaken for the House Fly, biting powers are attributed to 

 the latter which only belong to the former. 



All varieties have much in common to be explained, but we will first discuss the differences, 

 commencing with a description of the sucking apparatus of the House Fly. It will be seen extended 

 in the photograph on page 245, which represents the entire female insect, photographed from a 

 specimen prepared as a slide for the microscope, and therefore one compressed as flat as possible 

 in the mounting. Although this is the onlv way to get the whole insect into focus for the purpose 

 of photography, still it has the disadvantage of showing the proboscis in a manner that suggests 

 to the student it is a direct prolongation of the body. This, however, is not the case; it really 

 hangs down at right angles from it. [In another picture the lancets of the Stable Fly are shown 

 with their sheath; these hang down in just the same \\3.y and serve to explain the arrangement.] 



Pholo 6b] [J. h. Crailree. 



THE HOUSEFLY'. 



Although one of the commonest objects of our everyday life, there are really few 



persons ^vho know anything about the structure and habits of this dangerous pest. 



