HOUSE FLIES AND BLUEBOTTLES 197 



It is sufficiently strong to be able to perforate a thin 

 garment and reach the skin beneath. Under a high 

 power of the microscope its whole surface, except the 

 extreme tip, is seen to be beset with excessively minute 

 hairs. 



All the five species of flies of which we have hitherto 

 been speaking pass through practically the same series 

 of changes in the course of their life. The long oval 

 eggs are produced in great numbers, and are laid on the 

 substances which are to serve as food for the larvae. 

 This is different in different cases. The bluebottles 

 select flesh, either raw or cooked, and even wounds in 

 the living animal are not exempt from their attacks. 

 The frightful story of "Old Prue " in "Uncle Tom's 

 Cabin " has had its counterpart in real life, and the 

 torments of the wounded on a field of battle have some- 

 times been increased in this loathsome way. In the 

 summer time no animal substance can be long exposed 

 without being visited by these and other flesh-devouring 

 flies; but if it is in the open air, the chief visitor is 

 likely to be the flesh-fly, Sarcophaga carnaria, a voracious 

 devourer of animal matter, which, however, rarely enters 

 houses. It is quite different in appearance from these 

 others, being prettily chequered with black and white. 

 The larger house fly does not select meat, but deposits 

 its eggs amongst stable refuse, as the larvae feed upon 

 horse dung, of which they eat the softer decaying parts 

 and leave the bits of hay and straw. The smaller house 

 fly (H. canicularis) selects decaying vegetable matter; 

 but Stomoxys, like M. domestica, prefers the manure 

 heaps. 



Closely connected with the extraordinary nature of 

 the food of the Iarva3 is the rapidity with which these 

 flies pass through the earlier stages of their life. As an 



