INSECTS IN RELATION TO PACKING HOUSES 457 



and lard refineries at packing houses, is also used at some plants with 

 fairly good results, if the earth is thoroughly mixed with the paunch 

 manure and waste, or is used as a covering. Spent fuller's earth, when 

 it is discarded at the refineries, contains about 8 per cent of oil and acts 

 as a larvicide besides being a repellent for several days. In experiments 

 at a Dallas packing house a saturated solution of arsenic was also found 

 to be very efTective for killing larvae in paunch manure. 



Many other breeding places of importance exist around the plants, 

 such as the hog hair, tankage, blood cooking, and drying rooms ; in ferti- 

 lizer buildings ; along fertilizer loading docks where pulverized tankage 

 and blood and bone meal accumulate on the ground under the docks ; and 

 along car tracks where the soil becomes moistened by rain or by open 

 sewage disposal lines, quite often found under such docks. Often the soil 

 so covered with moist animal matter is found to be heavily infested with 

 blow fly larvae. Borax treatment for such infestations is very effective but 

 must be repeated frequently as fresh material is always accumulating and 

 is readily reinfested. Crude oil or fuller's earth applied heavily on such 

 breeding places packs the soil down well and also renders it less attrac- 

 tive for flies for a much longer period. It has repeatedly been observed by 

 the writer that where enough oil or fuller's earth had been applied there 

 was no fly breeding going on. When the capacity of a packing plant is 

 overtaxed, or when labor is short, large stores of bones and hog hair do not 

 get thoroughly dried in the hot air driers and these then become heavily 

 infested with blow fly and skipper fly larvae. The same condition is also 

 often found in storage houses containing bones, hair, blood, and tankage 

 that have been thoroughly dried, but again moistened by water leaking 

 through a bad floor or bad roof above. To pi'event fly breeding in any 

 of this material it must be thoroughly dried and then stored in an abso- 

 lutely dry place. 



Another common source of fly production found at packing plants is 

 under and around stick-water vats where the glue stock is manufactured. 

 Steel and wooden vats are used for boiling stick-water and sooner or 

 later these vats may become leaky or are heated to such an extent that 

 the stick-water boils over and saturates the soil below. Prolific fly breed- 

 ing then takes places. Borax solution or crude oil treatment for such 

 infestations is very effective. In the stock yards the hog pens are usually 

 all paved and the manure is washed into sewers leading to a nearby stream. 

 In many instances the sewer outlet is not directly into the water and the 

 manure is deposited in large quantities along the banks of streams where it 

 becomes heavily infested with fly larva> which develop in the moist manure, 

 thence migrating to dry places for pupation and emergence. The manure 

 mixed with hay and straw from cattle pens is usually hauled to nearby 



