48 



BULLETIN 1453, U. S. DEPARTMENT OF AGRICULTURE 



very probable that eggs are occasionally laid on cured meat while 

 it is drying in the smokehouse. There follows the question as to 

 whether any eggs so laid, or laid in times of favorable temperatures 

 during intermittent smoking, can survive the subsequent high tem- 

 peratures, heavy concentration of smoke, and smothering effect of 

 melted fat. Nothing very definite can be said with respect to this 

 point, principally on account of the lack of uniformity in the degree 

 and duration of the heat produced. In some cases (fig. 10), the heat 

 would be expected to kill any adults, eggs, or young larvse which 

 might be present. 



Throughout the warm months it is clearly apparent that one of 

 the most important flaws in our defense against skipper infestation 

 consists in the commonly unprotected condition of smoked meat dur- 



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July 5-7 Jaiy3l-Aag.2 



Fig. 10. — Reproductions of thermograph records of smokehouse temperatures. The 

 scale marked on the 40-degree line measures 4-hour intervals 



ing the second part of its stay in the smokehouse. From the time 

 the heat drops below 100° F. for the last time until the meat is re- 

 moved from the smokehouse there is a period of temperatures favor- 

 able to egg laying. The above diagram (fig. 10) gives a num- 

 ber of smokehouse records 5 , with the approximate range of repro- 

 ductive temperatures shown by the wide interval between 60 and 

 100° F. 



As shown in this diagram, there was usually abundant oppor- 

 tunity, so far as temperatures were concerned, for the flies to oviposit 



5 Pantograph copies of thermograph records obtained through the interest and courtesy 

 of E. Z. Russell, in charge of swine investigations. Animal Husbandry Division, Bureau of 

 Animal Industry. The writer is also indebted to K. F. Warner, of the swine investiga- 

 tions, and to G. A. Anthony, inspector, Washington Center Market, Bureau of Agricultural 

 Economics, for valuable cooperation in many ways. 



