50 BULLETIN 1453, U. S. DEPARTMENT OF AGRICULTURE 



reverse is true when they are fed and mated. In midsummer males 

 in breeding vials lived an average of 8.5 days and females 5.1 days. 



Male flies are slightly more numerous than females and they 

 usually require less time for metamorphosis. Both sexes are at- 

 tracted to light, but this stimulus is not a dominant one in the pres- 

 ence of food odors. 



The eggs hatch in about 21 hours at 80 to 90° F. and the larvae 

 cluster together for feeding. There appear to be three larval instars. 

 All stages of the larvae are repelled by light. 



After the completion of feeding the full-grown larva leaves its 

 food and seeks a dark, dry spot for pupation. The larval and pupal 

 stages are each five days long in hot weather (80 to 90° F.) when 

 fed on juicy ham. The life cycle occupies a minimum of 12 days, 

 and at Washington the average rapidity of summer increase is two 

 generations per month. The range of temperatures at which repro- 

 duction takes place is approximately 56 to 102° F. 



Control suggestions come principally under four heads : 



1. Preventing adults from enterino- storage rooms. This may be 

 accomplished by careful screening with 30-mesh wire cloth and by 

 using care that flies do not enter when the doors are opened. 



2. Preventing infestation of meats in rooms to which the flies have 

 access. The usual method consists of wrapping each piece of meat in 

 paper and inclosing the whole in a tight cloth sack, often with a 

 coating of yellow wash as additional protection. On farms and in 

 retail stores a closet or cage with sides of 30-mesh wire cloth should 

 be provided for the storage of cured meat. On farms, such a cage 

 would render wrappings, sacks, and washes unnecessary. The 

 prevention of infestation is the essence of skipper control. 



3. Killing Piophila, easel in infested meats. The maggots are very 

 difficult to kill, especially when they are feeding in the moist interior 

 of pieces of meat. They are able to withstand extremes of tempera- 

 tures, starvation, and immersion in water and other liquids for pe- 

 riods which would be fatal to most insect larvae. Hydrocyanic-acid 

 gas fumigation causes heavy mortality among skippers in meat, but 

 even strong dosages are not certain to kill them all. Inspection of 

 suspected hams and shoulders can not be relied upon to disclose either 

 the minute, concealed eggs or all of the deep-seated feeding larvae. 



4. Killing Piophila casei in infested rooms. To kill all stages 

 nothing is better than strong dosages of hydrocyanic-acid gas (2 

 ounces of sodium cyanide per 100 cubic feet) applied for 21 hours. 



On account of the large number of skippers which may be produced 

 by a single piece of meat, it is advisable to destroy promptly all in- 

 fested meat which can not be reconditioned by trimming. Supplies 

 of bones should not be allowed to accumulate near stores of smoked 

 meats. 



Where curing and smoking operations are confined to the winter 

 months, in parts of the country where the temperatures are below the 

 minimum reproductive temperature of the skipper (about 56° F.) 

 the danger of early infestation is avoided. 



Smokehouses should be well screened. Meats stored in a well- 

 screened farm smokehouse should require no further protection of 

 anv kind. 



