40 BULLETIN 1453, TJ. S. DEPARTMENT OF AGRICULTURE 



the sixteenth day and ended on the thirty-third day. Thirty other 

 adults showed the first mortality on the thirteenth day and the last 

 on the twenty-eighth day. Fifty newly formed puparia kept in the 

 refrigerator at this temperature produced the first of 42 adults on 

 the thirty-eighth day and the last on the forty-fifth day. 



Of migrant larvae placed in a Petri dish in the refrigerator at 

 48 to 50° F. on September 17, 15 were still alive on February 11, 13 

 were alive March 15, and 1 was alive April IT after seven months' re- 

 frigeration. Another lot of larvae was placed on dry sifted earth in 

 a Petri dish October 17. A brief rise in temperature April 9 gave 

 some an opportunity to pupate, but one was still in the larval stage 

 May 8. Two adults emerged after June 13, showing that the insect 

 survived at this temperature for eight months. In another test, 

 begun January 14, in which several hundred larvae which had been 

 developing in a poor culture for about a month were used, 8 or 10 live 

 adults were observed August 15. 



Experiments with migrant larvae in a refrigerator show that the 

 duration of this stage of the insect may be considerably lengthened 

 by certain manipulations. After such larva? have been confined for 

 several weeks at about 48° F., their shrunken appearance indicates 

 that they have undergone metabolic losses, and this is further shown 

 by the readiness with which they begin feeding again when placed 

 on juicy ham. In a day or so the maggots again become full fed, 

 whereupon they migrate a second time. If they are then collected 

 at once and replaced in the refrigerator, the process may be con- 

 tinued, probably over a long period if the temperature is always kept 

 low enough to prevent most of them from pupating. 



In a sulphur dioxide refrigerating machine at about 32° F. — 

 Mature puparia were exposed in a sulphur dioxide refrigerating ma- 

 chine at 32° F. on March 15, after having been in the ice refrigerator 

 since March 2 at from 48 to 50° F. A sample of these puparia was 

 removed June 3, and emergence resulted after exposure to room 

 temperatures. This pupal period was therefore three months. 



About 50 adults were exposed on February 16, having been taken 

 from a temperature of 51° F. One of these survived until after 

 March 15, a period of one month. In another lot of 98 flies, one 

 survived 33 days and one lived 37 days. 



Full-grown larvae at 32° F. do not pupate. After removal to 

 room temperatures, following refrigeration for periods up to nearly 

 three months, puparia were formed which produced adults. 



Half -grown larvae, removed to 32° F. from a temperature of 86°, 

 were all dead after six weeks ; in another lot, with the same history, 

 three were alive after six weeks. 



Eggs refrigerated at 32° F. for periods up to two weeks hatched 

 with hardly an exception after removal to favorable temperatures. 

 In this test newly emerged and newly mated pairs were allowed to 

 oviposit on ham and then the adults and eggs were placed in refrig- 

 eration. Upon removal, after progressively longer periods of ex- 

 posure to cold, the adults were given favorable food and tempera- 

 tures. The females which were subjected to this degree of cold for 

 periods up to and including 10 days resumed the deposition of fertile 

 eggs. 



Eggs exposed to 32° F. for one month failed to hatch. 



