April, '17] BISHOPP: FLIES AND ABATTOIRS 275 



in the soil adjacent for great numbers of flies, and accidents leading 

 to the infestation of the ground or in case of accumulation of tem- 

 porary breeding materials it is necessary to use some larvicide. Crude 

 petroleum has been found very helpful in preventing breeding in these 

 temporary situations. Where the amount of the breeding material 

 is large, however, the oil does not succeed in killing all of the maggots 

 unless applied very freely and frequently. The application of crude 

 petroleum to the grounds of the packing houses also aids in keeping 

 down dust, which is an additional good feature. Where incineration 

 is not practiced, the use of borax on paunch manure and other breed- 

 ing media has been found satisfactory. It is also effective in treat- 

 ing temporary breeding places of various types. It has been used at 

 about the same rate as that recommended for the treatment of stable 

 manure. The prompt covering of breeding materials on dumps with 

 fuller's earth, which has been discarded after use in lard refining, has 

 been found to check fly breeding materially, but should be employed 

 only as a supplemental or temporary measure. 



On account of the attractiveness to flies of abattoirs and packing 

 establishments we hold that fly traps fill a very distinct place in con- 

 trol work under such conditions. While the Hodge type window 

 trap has been found of some value under certain conditions, in general 

 it seems best to attempt to attract the flies into traps on the outside 

 of the building rather than to catch them in the windows or within the 

 departments. The kind of bait used has to be modified to suit the 

 conditions and the species of flies present. The mucous membranes 

 from hog intestines (a by-product of sausage casing manufacture) 

 has been found to be by far the most attractive bait for blow-flies, and 

 also catches a large percentage of house-flies. On account of its odor 

 this material cannot be used around edible departments and in front 

 of the establishments. As has been explained, the house-fly predom- 

 inates in such situations and therefore stale beer or some other good 

 house-fly bait is satisfactory in these situations. The simple conical 

 trap as described by the Department has been found most effective 

 and durable. 



In wholesale markets and departments where edible products are 

 manufactured, it is important that practically all flies be excluded. 

 For this purpose, window screening is largely employed, but under 

 conditions which often exist these are not sufficient as the flies gain 

 entrance through doors which are being opened very frequently. 

 Blowing devices have been employed in such passage-ways with some 

 success, and Hodge traps or fly exits through the window screens are 

 helpful in keeping the number of flies on the inside to a minimum. 

 Other difficulties in fly exclusion are met with in keeping flies from 



