368 



AN ECONOMIC ENTOMOLOGY. 



of the Cecidomyidcs. They produce a Httle black fly, Piophila 

 casei, similar to the house-fly in appearance, but much smaller, 

 and the only way to protect provisions is to keep them con- 

 stantly covered. They sometimes become an intolerable nuisance 

 in smoke-houses, attacking ham, bacon, and the like during the 



sary to get rid of them. In the first place, windows should be 

 closely screened to prevent their entry from outside ; the walls 

 should be whitewashed frequently, so as to keep all crevices 

 filled up ; the floors should be kept clean, and should be as solid 

 and smooth as possible, to prevent the development of maggots 

 in crevices filled with greasy substances. The flies can be killed 

 by fumigating with tobacco or pyrethrum, and this should be 

 done by closing up the rooms tightly in the evening after work 

 is done, or on a Sunday or other day w^hen work ceases, and a 

 suflicient quantity of either tobacco or pyrethrum should be 

 burnt on live coals to completely fill all parts of the rooms. They 

 should be left tightly closed anywhere from eight to twenty-four 

 hours, and at the end of this time the flies will have been de- 

 stroyed, but the maggots will not, and it will be necessary to 

 repeat this operation two or three times, at intervals of (at most) 

 a week, to destroy the flies as fast as they hatch, and before 

 they have an opportunity to lay their eggs. In some cases bi- 

 sulphide of carbon may be used to fumigate ; but this must be 

 done when there is no fire on the premises, and the house 

 should be left closed twelve hours at least, and should then 



Piophila casei, parent of "skippers" in cheese, 

 etc. 



Fig. 423. 



process of smoking, or be- 

 fore they can be cased, and 

 the value of the provision 

 is frequently impaired by 

 the development of these 

 maggots. Where a house 

 is once thoroughly in- 

 fested, the flies are found 

 in swarms everywhere, 

 ready to attack the meats 

 as soon as there is the 

 least opportunity. Under 

 such circumstances thor- 

 ough measures are neces- 



