Muscidae 429 



Feeding and care of immature stages. The larvae are reared in a 

 No. 2 galvanized tub on a mash consisting of 100 cc. cheap molasses, 

 % cake yeast, 5 pounds crushed oats, and 1 gallon water. The mash 

 is allowed to ferment for 4 days at a temperature of 30 C. (86° F.) 

 before the eggs are added. Three or four thousand normal-sized flies 

 may be reared on a tub of the mash. Two methods are employed in 

 obtaining eggs. The first, used when stock cultures are desired, is to 

 place a small pan of fermented mash in the cage for 5 to 10 hours. The 

 second method, employed when large numbers of eggs are desired within 

 a comparatively short period, consists in confining the gravid females 

 in vials plugged with cotton which has been moistened with 0.1% 

 ammonia water. 



The eggs are placed in the fermented mash and the tub is covered 

 with cloth to prevent contamination. By the time the larvae reach 

 maturity the upper layer of the mash will be sufficiently dry to permit 

 pupation. 



Just before emergence begins a special cover is placed over the tub. 

 This cover consists of a piece of cloth fastened between two pieces of 

 1" x 4", one slightly shorter than the diameter of the tub and the other 

 slightly longer than the diameter of the tub to support the weight of the 

 cage. There is a 2-inch hole in the center of the 1" x 4" boards, and a 

 similar hole in the bottom of the cage. If the cage is placed on the tub 

 so that the two holes match, and if the edge of the tub is darkened, 

 the flies will go directly into the cage. 



If the flies are to be used for experimental purposes, the cage is in- 

 verted and darkened, causing the flies to come back out the same hole 

 by which they entered. 



Temperature and light. Although sunlight is not essential for the 

 completion of the life cycle, it shortens materially the length of the 

 pre-oviposition period. High temperatures are fatal to the eggs, only 

 a small percentage hatching at 99 F. The larvae will continue to 

 feed at 99 F., but at 104° F. they discontinue feeding and concentrate 

 on the upper surface of the media. At 99 F. the mortality of caged 

 adults is high, even though plenty of water is available. A temperature 

 of 86° F. has been found very satisfactory for rearing all stages. 



REARING THE HOUSE FLY, MUSCA DOMESTICA, 

 THROUGHOUT THE YEAR 



Henry H. Richardson, U. S. Bureau of Entomology and Plant Quarantine 



THE rearing of house flies throughout the year for use in various 

 lines of biological research has developed largely in the last decade. 

 Formerly they could be reared in the northern states only from April 

 to December (Glaser, 1923, 1924) as horse manure, which was used as 



