1899] CHEESE AND BACON FLY. 9 



its mouth-hooks, grai')ples by means of them with the hinder edge of 

 the truncature, and, pulHng hard, suddenly withdraws them, jerking 

 itself to a distance of four or five inches." The length of the skips is 

 variable, but the unpleasant habit is only too observable. 



When full grown the maggot is stated to move from where it fed 

 to some comparatively dry spot, as, for instance, the wrapper of the 

 Cheese, or possibly of the Ham, where it has been feeding, and there 

 it contracts to about a fifth or sixth of an inch in length, and first 

 changes to a yellow tint, then to a golden or red brown, the outer 

 coat becoming hard and much wrinkled at the head extremity, and 

 still more so at the tail. This puparium, or chrysalis-case, is elliptical, 

 about a fifth of an inch in length, and from this the fly emerges in a 

 time that may vary from thirty-six or forty-eight hours to from eight 

 to ten days. The longer time is given in German observations, the 

 shorter in U.S.A. observations, and the variation may probably depend 

 on weather and temperature. In observations on the life-history by Dr. 

 Kessler, he found that the average time in developing from egg to fly 

 condition is four to five weeks, with two or three generations during 

 the summer, the last generation occurring in September, and the 

 maggot passing the winter in the puparium — that is, in the brown 

 chrysalis-case, and turning to the pupal state within it in May. 



The chief points of the habits of the infestation, as given by com- 

 parison of the published information of the United States and European 

 records, together with some notes of observation of attack both to 

 Cheese and Bacon in this country, may be condensed into a small 

 compass as follows. 



The infestation (Piophila casei) may pass the winter either in fly or 

 in chrysalis state in any convenient place, as in crannies, crevices, 

 behind boards, anywhere, in fact, where it can hide away, and from 

 these shelters, unless exposed to " severe and protracted cold," by 

 which (it is said in recent observations) " larvas, pupte, and flies are 

 killed," the flies come out in spring. The first application which I 

 received in the past season regarding attack was sent me on the 29th 

 of March, with the remark that the Cheese-room " is swarming with 

 them now." 



The flies chiefly select for egg deposit Cheese and cured meats, as 

 Ham and Bacon, and to some (though a much lesser) extent. Salted 

 Beef. Rich, or, as it is sometimes called, " fat," Cheese appears to be 

 especially preferred, and they likewise attack cream Cheese. There 

 appears no doubt that it does not lay eggs on fresh meat, and Smoked 

 Beef is "to some extent" subject to attack, but Ham and Bacon are 

 the special subjects for egg-laying so far as concerns cured meats. 

 The details of nature or condition of material — namely, of the Cheese 

 and salted, or smoked ; or salted and smoked Pork — chosen for attack, 



