244 INSECT ARTIZANS AND THEIR WORK 



to become flies, all the female flies do not become 

 mothers ; but to eliminate failures of this sort he 

 reckons that half a generation consists of females 

 and that each female lays only 120 eggs instead of 

 her maximum 600. 



He shows that in the United States, at least, 

 typhoid, cholera infantum, and " summer com- 

 plaint " are chiefly spread by these flies carrying 

 the germs from the sick to the well. Most other 

 complaints that flesh is supposed to be heir to are 

 greatly assisted in their spread by the same agency. 

 Several English authorities on sanitation have made 

 similar declarations as the result of their investiga- 

 tions. 



Many of these creatures are a sort of Jekyll-and- 

 Hyde combination of two personalities, here, how- 

 ever, marking two successive phases of existence. 

 The question is which is the greater, the harm or 

 the good they do ? The answer for the individual 

 may be the harm, whilst for the race it is probably 

 the good. Any way, the rational course is to clear 

 away the cause, and the effects must cease. The 

 stable is rapidly becoming an institution of the 

 past. Let the suburban gardener anticipate the 

 early date when it will have ceased to be by feeding 

 his garden with chemical manures. 



But one of our House Flies (Homalomyia canicu- 

 laris) a somewhat smaller and paler insect' than 

 the other feeds in its larval days on decaying 

 vegetable refuse, so the garden rubbish should be 

 burnt, not stacked. This fly has more rounded 



