DIPTERA. 



179 



petty injury they inflict in our larders, must be looked 

 upon as being among the most important agents employed 

 in the police of Nature. Death is everywhere abroad, 

 but the earth is not permitted to be long defaced by the 

 presence of decay. No sooner does the carcase fall, than 

 these, 



** The swiftest of His winged messengers," 



are set to work, and speedily remove the offensive carrion. 

 Linnaeus asserted that three flesh flies could devour a 

 dead horse in less time than it would take a lion to effect 



FlG. 139. METAMORPHOSES OF FLESH FLY. 



the same object ; and a little consideration will show that 

 the expression is not exaggerated. The hungry lion can 

 but make a meal, and then must wait for his returning 



FIG. 140. DOMESTIC FLY. (Magnified.*) 



appetite. The flesh-fly brings her twenty thousand 

 young ones, ready for the work. Each of these for five 

 days is constantly employed ; and when we consider that 



