Volume VIII JUNE, 1921 No. 1 



THE PROTECTION OF MEAT COMMODITIES 

 AGAINST BLOWFLIES 



By R. a. WARDLE. 



( University of Manchester. ) 



A SURVEY of the literature concerning the economic aspect of the Muscid 

 genera comprised in the popular term "blowfly" will indicate that, 

 although much work has been carried out with respect to the prevention 

 of oviposition upon living animals, and although several recent papers 

 have dealt very fully with the problem of trapping or poisoning Muscid 

 flies in general, yet the question of directly preventing oviposition upon 

 foodstuffs has been neglected somewhat and its importance overlooked. 



In Manchester, the alternate periods of fine rain and sunshine that 

 constitute a normal summer are especially favourable to blowflies. 

 Swarms of such flies are particularly noticeable in those shops — butchers, 

 fishmongers, fruiterers and the market stalls — where, from motives of 

 ventilation, the window space is not enclosed by glass. In such shops 

 the usual methods of fly-prevention are impracticable. Poison bait traps 

 do not enhance the appearance of a window containing food commodi- 

 ties. Screens of mosquito netting impede the circulation of air, so 

 necessary in this type of shop, and becoming quickly soiled by juices of 

 meat or fruit, obscure the view of the purchaser. 



Attempts at fly-exclusion are therefore almost non-existent. The 

 butcher will assert that his meat rarely becomes flyblown, a statement 

 based generally upon the popular belief that only tainted meat is 

 attacked by blowflies, but supported somewhat as a fact by the custom 

 of keeping meat overnight in a refrigerator and placing it upon the 

 boards of the open window in a slightly chilled and coagulated condition. 

 The fishmonger is protected to some extent by the use of ice slabs and 

 the hose-pipe. The fruiterer is frankly indifl'erent. 



Conditions conducive to oviposition. 



The factors which affect oviposition fall readily into two categories : 

 {a) nature of the foodstuffs attacked, (6) meteorological conditions. 

 The range of substances attractive to blowflies is wide, comprising 

 Arm. Biol, vm 1 



