GENERAL LIFE HISTORY 41 



extrusion, which it uses as a punching and pushing 

 machine. 



After emerging from the ground, the fly withdraws 

 the bag-like extrusion and cleans itself. Its body soon 

 grows fit and it becomes very active, as long as day- 

 light and warm weather favour it ; otherwise it seeks 

 shelter and becomes quiescent ; however, artificial 

 light and heat will awaken it to nocturnal activity. 

 Sweets, carrion, and filth are all attractive to the blue- 

 bottle, but the house-fly and the lesser house-fly also 

 find extraordinary attraction in both man and his 

 dwelling. 



Considering the superfluity of other flies, and the 

 multitude of other insects ever ready to do duty as 

 devourers of carrion, garbage, and filth, the scavenging 

 services of the larvae of the house-fly can be well 

 dispensed with. 



In civilised communities cremation in a refuse 

 destructor is the only'sanatory method of treating town 

 refuse. The economic value of the fly is very little, 

 and consists merely in its food value for certain birds. 



In warm weather the scavenging capabilities of all 

 the carrion and filth feeding maggots are very remark- 

 able, and there appears no exaggeration in the state- 

 ment by Linnaeus, that the progeny of three flesh flies 

 can eat up the carcase of a horse sooner than it could 

 be devoured by a lion. 



When a batch of eggs has matured in the abdomen 

 of the female, she is most careful in the location and 

 manner of their disposal. Guided by the sense of 

 smell, she will not lay her eggs except in contact with 

 food, or in places securing her progeny access to their 



