6 BULLETIN 1453, U. S. DEPARTMENT OF AGRICULTURE 



obtained. Although dealing with conditions not found in the United 

 States, the following paragraph, an abstract of pertinent parts of 

 his report, is of interest because it emphasizes the power of increase 

 and destruction inherent in the cheese skipper in the presence of an 

 unlimited food supply resulting from careless sanitation : 



Very large quantities of fish are smoked at the Astrachan fisheries, but on 

 account of the ability of the cheese skipper to infest this product the smoking 

 is discontinued in summer. Fish packed in barrels and covered with brine 

 has been very severely attacked by the insect, which is the chief pest and the 

 only dipterous enemy of fish preserved in this way. Because of the use, during 

 the Great War, of imperfectly seasoned lumber to make the barrels, cracks 

 appeared in the latter as they dried, allowing the brine to leak out. The eggs 

 of P. casei were laid in the moist cracks thus formed and the young larvae en- 

 tered the barrels, often reducing the contents to a formless mass of flesh and 

 skeletons. On account of the war, also, the ice supply in the storage houses 

 was below normal and this condition promoted increase of the pest. At one 

 plant the puparia among and under the barrels of fish could be gathered by 

 the shovelful ; in another ice house the floor was so covered with puparia 

 that it resembled the floor of a grain elevator. 



Sakharov also stated that the insect attacks green sealskins. 



A list of the food materials of the larvae and adults which are re- 

 ported in the literature of Piophila casei includes cheese, bacon, 

 ham, human excrement, rotten fungus, human corpses (both buried 

 and exposed), oleomargarine, smoked beef (also known as dried beef 

 or beef hams), putrid beefsteak, salted beef, hoofs, horns, dried 

 bones, moist hog hair, smoked fish, fish in brine, and green sealskins. 

 Verbal reports to the writer state that infestations have been known 

 to occur in marrow bones and in lard. Common salt and water glass 

 are recorded as larval foods, but these records are open to question. 

 It should be noted, also, that flies of other species of Piophila (imma- 

 ture forms unknown), closely resembling P. casei, occur out of doors: 

 consequently some recorded observations may have been incorrectly 

 assumed to relate to the cheese skipper. Furthermore, larvae of 

 certain flies of the families Ortalidae and Drosophilidae and of the 

 genus Lonchaea also possess the ability to skip, according to C. T. 

 Greene, of the Bureau of Entomology. 



The writer has not succeeded in rearing skippers in the circum- 

 muscular fat of ham, and in general it appears that the generic 

 name Piophila (derived from the Greek Trior, fat, and ^>tAo?, loving) 

 is not strictly appropriate. The fat parts of cured ham are not 

 nearly so attractive for oviposition or feeding purposes as are the 

 lean portions and the connective tissue — points which will receive 

 further attention in this discussion. Both smoked herring and 

 salted herring supported the life cycle in the laboratory. Semi- 

 liquid putrid beef, Bologna sausage, several varieties of cheese, the 

 marrow of ham bones, and lean ham have proved suitable media. 

 An attempt to rear the insect on decomposing mushrooms was un- 

 successful, no progress was made by larvae in lard substitute, and a 

 number of trials with ham fat showed that it was entirely unfavor- 

 able as a food, although this may have been due partly to suffocation 

 of the larvae by the melted fat. 



A flask containing several thousand puparia, many of them in 

 a fermenting condition because of metabolic moisture confined in 

 the stoppered container, was observed to be infested with the mag- 



