390 Phylum Arthropoda 



a i% suspension of Harris brewers' yeast (dry powder) in the liver 

 extract, the mixture being tubed and autoclaved. If not more than 5 to 

 10 larvae are present in a tube containing 14 cc. of the liver extract-killed 

 yeast medium, the larval stage of Aedes acgypti, at a temperature of 

 2 7°-2 8° C, consumes about 8 days. 



Bibliography 



MacGregor, M. E. 1929. The significance of the pH in the development of 



mosquito larvae. Paras. 21:132. 

 Trager, W. 1935. The culture of mosquito larvae from living micro-organisms. 



Amer. J. Hyg. 22:18. 



References 

 For the rearing of mosquito larvae see also pp. 376, 383, and 386. 



Family psychodidae* 



PSYCHODA ALTERNATA AND P. MINUTA** 



A STUDY of the breeding habits and life history of Psychoda alter- 

 nata was made with the view of determining whether it might not 

 be used for studies in genetics. The effort was attended with unusual 

 success both in breeding the flies and in the discovery of at least two 

 mutations. 



The adults are about 2 mm. in length. They ordinarily breed in decay- 

 ing vegetation, but dung from either horses or cattle has proved to be 

 an excellent medium. Breeding takes place readily under laboratory 

 conditions, the life cycle being completed in from 12 to 16 days. Adult 

 females are favorably stimulated by the culture medium, so that ovi- 

 position takes place quickly. The eggs hatch in a little less than 2 days 

 into active, eyed larvae resembling those of midges. The larvae feed 

 for about 10 days, after which they become quiescent and pupate. 

 Adults emerge 2 days later. 



Pedigreed strains were maintained in test tubes and small flasks, while 

 battery jars were employed for large mass-cultures. 



M. E. D. 



* Editor's Note: The reader may find an excellent summary of what is known of the 

 biology of other members of this family in an article entitled Aquatic Diptera Part I. 

 Nemocera, exclusive of Chironomidae and Ceratopogonidae, Cornell University Agricul- 

 tural Experiment Station Memoir 164, pp. 23-24, 1934, by O. A. Johannsen. 



** Abstracted from an article in Science 60:338, 1924, by C. L. Turner, Beloit College. 



