THE CHEESE SKIPPER AS A PEST IN CURED MEATS 45 



pupa?, and unprotected larvae have been killed by exposure to the 

 same dosage for 23 hours, during which period the temperature fell 

 from 65 to 55° F. 



Any process used for killing skipper maggots in cured meats 

 should of course be followed by cutting out infested parts. 



KILLING PIOPHILA CASEI IN INFESTED ROOMS 



According to Murtfeldt (53, pp. 174,-175) the fumes of burning 

 sulphur or pyrethrum powder kill the adults. One firm with which 

 she corresponded whitewashed infested rooms after fumigation, using 

 carbolic acid in the whitewash. Howard (32, p. 10^) suggested that 

 infested places be washed with kerosene emulsion, special attention 

 being given to the cracks. Burning sulphur or pyrethrum on live 

 coals kills the flies if rooms are kept closed for from 8 to 24 hours 

 (Smith, 70, p. 368), but as this does not kill the maggots it should 

 be repeated. Smith also believed that carbon disulphide could be 

 used with good effect. 



Surface (72, pp. 21, 21±) suggested that badly infested rooms be 

 fumigated with hydrocyanic-acid gas, and Herrick (31, p. 292) 

 directed that such rooms be washed with kerosene oil. 



The writer found that strong dosages of pyrethrum powder or of 

 pyrethrum smoke almost completely paralyzed the adults after 10 

 to 15 minutes, and that death followed in about 2 days. Measure- 

 ments of the dosages used were not attempted. Migrant larvae were 

 placed in a mass of pyrethrum powder which was taken from a 

 freshly opened air-tight bottle, and 2 days later 22 of the 29 larvae 

 had pupated in the powder. Eighteen of these puparia produced 

 adults. 



Carbon disulphide, at the rate of 1 pound per 100 cubic feet for 20 

 hours, was tested as an insecticide for all stages. The temperature 

 was about 75° F. and the relative humidity ranged from 86 to 98 

 per cent. Some of the larvae (migrants) were not killed, but there 

 was no emergence from the puparia exposed to the gas. No progeny 

 developed from the eggs, and the adults were all killed. 



The vapor of carbon disulphide is inflammable and highly explo- 

 sive when mixed with air in certain proportions. There must be no 

 fire, or sparks of any kind, where fumigation is being carried on. 



Sulphur fumigation has been extensively used in the past for the 

 control of various insects, but it has now been largely superseded by 

 other fumigants, chiefly on account of its strong bleaching and tar- 

 nishing action in the presence of moisture and its harmful effects on 

 growing plants and on the germinating power of grain. Records 

 of the use of this fumigant against insects indicate that the method 

 has generally been effective. Although sulphur fumigation tests 

 with P. casei were not made in this investigation, it is probable that 

 strong fumes are fatal to this species except when the larvae are 

 imbedded in the tissues of meat. In tight compartments an effective 

 concentration of the gases from burning sulphur appears to be ob- 

 tained by the use of about 3 pounds of stick sulphur per 1,000 cubic 

 feet of space, with exposure for 24 hours. 



The most reliable method of treating infested rooms is thorough 

 sweeping followed by fumigation for 24 hours with hydrocyanic- 



