34 THE BOOK OF THE FLY 



kinds of flies and of the serious suffering of their horses 

 from the bites of the stable-fly. This lamentable ig- 

 norance was shared by the joint authors of " Humble 

 Creatures/' published in 1858, when Neo-Darwinism 

 was in vogue, and many books were published for 

 popularising a knowledge of common things and 

 spreading an interest in nature-study ; this publication, 

 which is still (1914) in print and very little revised, has 

 probably led some later would-be nature-study teachers 

 to follow suit in confusing the characteristics of the 

 two species. Very often the fly most numerously 

 breeding in the manure heaps of the mews will be 

 Borborus equinus, or some other of the same family, 

 which are characterised by a very simple pattern of 

 wing nervures and by the absence of squamae or scales 

 behind the wings ; also the ankle joints of the feet are 

 most peculiarly short and broad. B. equinus, and a 

 great host of other dung breeding flies of a still smaller 

 size, may be considered beneficial insects ; they do not 

 pester cattle, and their larvae make food more scarce 

 for injurious flies. 



The breeding habits of the blue-bottle are very con- 

 spicuous by reason of its haste and boldness in taking 

 possession of dead animals. It is incapable of breed- 

 ing in horse or cow dung, to which latter the green- 

 bottle fly often resorts. 



The blue-bottle deposits her eggs, 500 or 600, pre- 

 ferably on dead fish, or flesh, and sometimes on the 

 sores or the flesh of wounded animals, but both the 

 house-flies preferably affect dung, carrion, garbage, and 

 all kinds of fermenting vegetable matter. It has been 

 commonly but not truly said that the principal breed- 



