ENTOMOLOGY

458 SANITARY ENTOMOLOGYdumping grounds and is th-ere allowed to decompose, or is occasionallyburned over, but very seldom incinerated.Cockroaches arc found in the blood and tankage rooms, dressingrooms, and other departments that are not under refrigeration. Modernsteel and concrete construction has much to do with eliminating theseinsects. The use of steam and hot water in cleaning up the machinery,walls and floors of all the departments and rooms containing edible goodsdestroys most of them that come in during the night and do not returnto their better protect~d hiding places i~ the departments of inedibleswhere there are also good breeding places. Where steam and hot watercannot be used freely against roaches, the dusting of sodium :fluoride isvery effective. About four pounds of sodium fluoride, applied with a dustgun by the writer in a dry salt cellar and tankage drying room at acertain packing house, killed over 5,000 roaches and thoroughly cleanedaway the pest. A thorough inspection of these same departments monthslater revealed only a few roaches which probably came in from otherdepartments of the plant that were not treated.When skipper fly larvae are found in cured meats the products infestedare trimmed and the storage rooms thoroughly cleaned, or if the infestationis severe, the meat products are rendered for inedible purposes, theuninfested products removed and the storage rooms fumigated.PROTECTION AGAINST INSECTSThat flies can be kept out of packing houses to such an extent thatthey are not objectionable is well demonstrated in some of the largeplants at Kansas City, Missouri; Davenport, Iowa; Omaha, Nebraska;Milwaukee, Wisconsin, and Topeka, Kansas; which are completely andthoroughly screened and remain remarkably free from flies on the insidealthough flies are plentiful on the outside.For the protection of meats against skippers it is necessary to screenclosely with twenty-mesh wire. It is also necessary to keep the storeroomsdarkened. The use of fly traps around packing plants is fullyjustified. Even though everything possible is done to eliminate breedingplaces on the premises, great numbers of flies come from the surroundingdistrict to the attractive con(litions which are to be found around packingestablishments. Our investigations have shown that flies quickly come toslaughter houses when liberated at nearly a mile distant. No doubt theyoften travel much farther to such establishments. Traps of variousmodels are used extensively at packing plants and where traps are wellhandled great quantities of flies are captured. Accurate records kept bysome plants show that as high as !!85 pounds of flies were captured in