April, '17] BISHOPP: FLIES AND ABATTOIRS 273 



species concerned. In general, it may be said that the hlow-tiies give 

 greatest annoyance about the inedible departments of the establish- 

 ments and where fresh blood is present. While the house-flies also 

 exist under these conditions they are found in greatest numbers about 

 the portions of the plants where the finished products are to be found. 

 They are especially numerous about the various loading docks and in 

 sausage rooms. House-flies may also give annoyance in certain de- 

 partments where scarcely a blow-fly is to be seen. They are also veiy 

 troublesome in the wholesale markets connected with the packing 

 establishments. Although the kind and number of blow-flies vary 

 somewhat in different regions, it may be said, in a general way, that 

 the common black blow-fly, Phorniia regina, is the most troublesome 

 of this group. In the middle of the season it is often supplemented 

 or replaced b}^ the green-flies, Lucilia ccesar and L. sericata, and oc- 

 curring with it is the large bluebottle-fly, Cynomyia cadaverina, and 

 several species of Calliphora, notably erythrocephala, vomitoria, col- 

 oradensis, and iridescens. In the South the screw-worm-fly, Chry- 

 somyia niaceUaria, often becomes excessively abundant during the 

 summer season, while the other species mentioned are greatly reduced 

 in numbers or entirely disappear. Several species of Sarcophagids 

 are also in evidence during the summer months, but they are usually 

 not present in great numbers and seem less prone to enter buildings. 

 The black anthomyid flies, Ophyra aenescens and 0. leucostoma, are 

 sometimes present in considerable numbers, but are to be found only 

 rarely within buildings. The former of these is found only in the 

 Southern States. Fannia canicularis and scalaris are common, but 

 are not given to free visits to animal products. The skipper-fly, Pio- 

 phila casei, is usually present during the summer months about nearly 

 every establishment, but on account of the care exercised in protect- 

 ing cured meats it is seldom of any particular importance except in 

 branch houses where it often causes considerable loss. 



The three species of cockroaches commonly found in the United 

 States are present in greater or less numbers about packing houses. 

 Their abundance and the consequent danger of contamination of food 

 products by them is greatly lessened by the construction of buildings 

 of steel, concrete and brick. In some of the older plants they are a 

 source of much annoyance. 



The ham and hide beetles, like the skipper-fly, seldom do any ma- 

 terial damage to products about the establishments, due to care ex- 

 ercised in handling material subject to their attack. They have been 

 reported as doing considerable damage to products in branch houses 

 and about small establishments not under government supervision. 



