43° Phylum Arthropoda 



the larval medium, was found deficient in nutritive value during the 

 winter months. R. W. Glaser (1927) found that the addition of small 

 amounts of baker's yeast to horse manure made it possible to rear the 

 flies during the winter. Grady (1928) developed the technique of 

 rearing large numbers of flies for daily insecticidal tests and by use of 

 Glaser's method was able to rear flies continuously throughout the year. 

 However the use of horse manure or mixtures of it with hog manure 

 (Hockenyos, 1931) as a rearing medium has several disadvantages. It 

 is not always available to most laboratories and also it is rather dis- 

 agreeable to use. Most important is the fact that frequently a species 

 of red mite parasitic on the house fly (probably of the genus Trom- 

 bidium) is brought in on horse manure. As many as 40 or more mites 

 will attack one house fly and the presence of these mites of course pre- 

 cludes the use of such parasitized flies for experimental work. The 

 writer (1932) developed a medium of wheat bran and alfalfa meal 

 which was found suitable for rearing the larvae throughout the year. 

 The materials needed are readily available to most laboratories; they 

 are free from parasitic mites; and are clean and easy to handle. The 

 preparation of the medium is as follows: 



Wheat bran t>-Va lbs. 



Alfalfa meal 1-^4 lbs 



V Mix thoroughly 



Water 5000 cc. -> 



Yeast suspension* 300 cc. I Mix thoroughly 



Diamalt** 25 cc. J 



Add the water mixture to the bran mixture and stir thoroughly. The 

 amount of water used in the medium is of considerable importance and 

 depends to some extent on the type of rearing jar used and the tightness 

 of the cover. Tall narrow-mouthed containers need less water as evapo- 

 ration from such jars is less. The amount of water should be such that 

 the medium will dry out on top as incubation progresses, as the mature 

 maggots pupate here. If too much water is used the top of the medium 

 remains wet and the larvae will tend to migrate out of the jar in their 

 effort to find a dry place for pupation. Trouble with fungous growths 

 may also be experienced. The medium may be used as soon as prepared. 



The equipment needed for rearing a large steady supply of house 

 flies throughout the year includes: A room in which temperature may 

 be kept approximately constant near 8o°-85° F. to be used as the 

 insectary or breeding room; a supply of small wire-screened cages in 

 which to keep the adult flies; and a number of rearing jars or pails. A 

 room 8 x 12 ft. should be sufficiently large in which to raise 2000 or 



♦Prepared from i lb. baker's yeast to 2 liters of water. This stock suspension should 

 be kept on ice and used as needed. 



**A malt sugar concentrate made by the Fleischmann Yeast Co. 



