434 Phylum Arthropoda 



Certain extraneous dipterous species were occasionally present in 

 the cultures, but had no apparent detrimental effect. 



Two species of mites, whose adults were ectoparasitic on the adult 

 flies, were sometimes present in the medium, but only attacked the 

 emerging adult flies in those cases where larval development was re- 

 tarded, giving the mites time to mature. 



When flies were due to emerge (7 to 12 days after pupation), the 

 pans containing them were placed under the emergence cages. These 

 were more or less funnel shaped cages, made of screening, 8 meshes to 

 the inch. They were left open at the wide end, to be placed on a flat 

 table, and had a screen cap fitted over the small end. By placing a 

 black cloth around the cage the flies were induced to ascend to the 

 light and were removed via the screen cap. 



A factor to be considered in winter rearing was the tendency of the 

 adult females to develop enlarged fat bodies for hibernation, and to 

 cease oviposition. Hence it is advisable to secure eggs from young 

 females and to rear other generations as soon as possible. In summer, 

 females may continue to oviposit for 6 weeks. 



Family borboridae 



j 



borboridae * 



INTEREST attaches to forms easily reared throughout their life cycles 

 in the laboratory because of their possible value both in the class- 

 room and in research work. During a study of certain insects found 

 about sheep manure, the ease was noted with which two species of 

 Leptocera (Limosina) were carried through from generation to genera- 

 tion in milk bottles or shell vials, when sheep dung was used as 

 food. 



The two species studied, Leptocera longicosta and L. or dinar ia, belong 

 to the family Borboridae and are not distantly related to the Drosophi- 

 lidae. In size also they approximate the smaller fruit flies. At Princeton 

 summer temperatures the former completes a life cycle in n to 14 

 days, the modal period being 12 days, while that of the latter is shorter 

 at 9 to 10 days. They are handled in transferring after the manner 

 familiar with fruit flies, being positively phototropic and withstanding 

 etherization well. It is probable from our observations on nearly a 

 dozen generations that they may be maintained indefinitely by suc- 

 cessive transfers. While only two species are here discussed, additional 

 species of the same family were encountered in our catches out-of-doors, 



♦Reprinted with slight changes from an article in Science 69:577, 1929. by J. W. 

 Wilson and Norman R. Stoll, Rockefeller Institute for Medical Research. 



