THE CHEESE SKIPPER AS A PEST IN" CUEED MEATS 



43 



High temperature in hot water. — It is possible to assemble accurate 

 information regarding the resistance of migrant larvae of Piophila 

 casei to heat by immersing them in hot water. In experiments of this 

 kind the only apparent variable is the heat, which can be closely 

 regulated and which reaches the larva? without passing any insulat- 

 ing barrier such as is present when maggots are exposed in vials to 

 hot air. In Figure 9 the results of a number of trials with migrant 

 larvae are plotted. The position of the dots (fatal immersions) and 

 circles (immersions not fatal 24 hours after removal from the water) 

 defines the approximate location of a mortality curve for this species. 



Each test shown in Figure 11 was made by holding about 10 larva? 

 in a coarse strainer immersed in several gallons of water. Inasmuch 

 as immersion in water of room temperatures has no effect on the 



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120 



Fig. 9. — Mortality curve for migrant larvae of Piophila casei immersed in hot water. 

 The dots represent experiments in which all were dead 24 hours after immersion ; 

 the circles indicate trials which resulted in either continued activity or metamor- 

 phosis at the end of 16 days ; the tests which were not fatal after 24 hours hut 

 which showed 100 per cent mortality after 16 days are shown as circles crossed 

 by a diagonal line 



larvae even if continued for two or three hours, the drowning action 

 of the water in the tests is not considered to be the primary cause of 

 death. 



Hot water transfers heat to meat more rapidly than does hot air, 

 but in attempting its use as a skipper larvicide two possibilities 

 must be guarded against — leaching the meat and cooking it. The 

 temperature should be high enough to provide for a brief though 

 fatal period of immersion, yet not so high as to produce a noticeable 

 cooking effect. 



According to information compiled by the meat inspection division 

 of the Bureau of Animal Industry, commercially cooked hams are 

 not usually boiled but "are cooked at temperatures as low as 155° F., 

 a temperature of about 170° being commonly used. It is evident, 

 then, that the maximum useful temperature for killing skippers in 



