PHOTOPERIODIC CONTROL OF DIAPAUSE IN THE 

 PITCHER-PLANT MIDGE, Metriocnemus knabi' 



OSCAR H. PARIS, JR.-, AND CHARLES E. JENNER 



Department of Zoology, University of North Carolina, 



Chapel Hill, North CaroUna 



The widespread occurrence of the phenomenon of photoperiodism 

 among both plants and animals makes its study a matter of consider- 

 able biological importance. Thus far knowledge has advanced most 

 rapidly in the case of plants, perhaps owing in part to the more suit- 

 able nature of plants for experimentation. A search among animals, 

 therefore, for favorable experimental material for the investigation of 

 photoperiodism seems particularly desirable at this time. The present 

 paper reports our progress in the study of the photoperiodic response 

 of the pitcher-plant midge, Metriocnemus knabi, a species offering 

 many advantages as an experimental animal for photoperiodic re- 

 search. 



Surprisingly few photoperiodic studies, and none of a compre- 

 hensive nature, have been made on dipterous insects, despite the fact 

 that one of the earlier reports on insect photoperiodism concerned 

 this group (Baker, 1935). The photoperiodic control of the termina- 

 tion of diapause (i.e., developmental arrest) has been reported for 

 the winter eggs of Aedes triseriatus (in Canada, Baker, 1935); for 

 the hibernating larvae of the mosquitoes Aedes triseriatus (in Georgia, 

 Love and Whelchel, 1955), Anopheles barberi (Baker, 1935), 

 Anopheles claviger (Kennedy, cited by Andrewartha, 1952), and 

 Wyeomyia smithii (Jenner, 1951); and for the hibernating larvae of 

 the ceratopogonid midge, Culicoides guttipennis (Baker, 1935), the 

 phantom larva Chaoborus sp. and the pitcher-plant midge Metri- 

 ocnemus knabi (Jenner, 1951). Normal autumnal hibernation was 



1 This investigation was supported by a research grant (E-356) from the 

 National Institute of Allergy and Infectious Diseases, Public Health Service. 



2 Present address: Department of Zoology, University of California, Berkeley 

 4, California. 



601 



