72 THE BOOK OF THE FLY 



" Destruction and Prevention of Household Pests," 

 Dr. Gay advised rich and poor, in every household, 

 whether or not a sanitary dust-bin was in use, instantly 

 to wrap up in paper all such fly-breeding materials in 

 readiness for cremation. However, to do so would be 

 missing the much more effectual course of applying 

 my "egg-trap' 1 plan of collections in exposed open 

 bags for cremation on the third day. 



For indoor use insecticide methods are more suited ; 

 and the best of these are immensely more effective than 

 some popular devices, which make a remarkable dis- 

 play and sell well, but which the purchasers soon 

 become neglectful to keep in constant use. Traps in 

 the form of wire-gauze cages, and glass non-return 

 bottles belong to this latter class of contrivances; when 

 seen crowded with struggling victims, the employment 

 of such articles captivates many observers ; but their 

 real efficiency will be found to fall far short of general 

 expectation. The explanation will be apparent when 

 the use of the \vire-cage trap is contrasted with the 

 success of a good fly poison. Given, say, a dwelling 

 room on a midsummer day containing ten female flies 

 and ten idle dancing male flies ; in such cases not 

 more than half the females and one quarter of the 

 males will get imprisoned within four or five hours by 

 the employment of the wire-cage trap, but with a good 

 method of setting poison nine-tenths of the females 

 and half the males may be killed within the same 

 period. In the case of poisoning, the dead have to 

 be swept up, whilst fly traps have the advantage of 

 collecting the victims ; but, unless the inmates are 

 carefully destroyed, a few will manage sometimes to 



