866 F. RÔMER UND S. ROSIN 



SUMMARY 



1. The daily swarming periods of Chironomus plumosus were taped und * 

 spécial considération of light intensity and température at the lake of Wohh 

 (46° 58' N; 7° 19 E) from the beginning of May till the middle of October. 



2. Ch. plumosus is swarming during the great change of light intensity 

 disk and dawn. 



3. In spring and autumn Ch. plumosus is swarming before sunset, in summ 

 after sunset; this graduai shift of the swarming period in the course of a ye; 

 corresponds to a shift in the scope of the light intensity in which the midges a' 

 swarming. 



4. There is a slack négative corrélation between the température of the a 

 and the light intensity at the peak stage of the swarm; and there is a somewh. 

 tenser négative corrélation between the température of the water of the lake 

 Wohlen during the last period of development of swarming midges and the ligl 

 intensity. The best corrélation (r = — 0,91) results from a linear combination < 

 the two températures. 



5. The most important factors determining the swarming period are coverej 

 with the light intensity at the peak stage of the swarm and the two (above mer 

 tioned) températures. 



6. It is discussed how air- and watertemperature could modify developmei 

 and function of the compound eye of Chironomus and in what way eye develot 

 ment could cause the shift of the daily swarming period. 



LITERATUR 



Eidmann, H. 1970. Lehrbuch der Entomologie. Hamburg und Berlin, P. Parey. 

 Fischer, J. \969a. Das larvale Wachstum von Chironomus nuditarsis Str. Rev. suiss 

 Zool. 76: 727-734. 



— 19696. Zur Fortpflanzungsbiologie von Chironomus nuditarsis. Str. Rev. suiss 



Zool. 76: 23-55. 



— und S. Rosin. 1968. Einfluss von Licht und Temperatur auf die Schliipf-Aktività 



von Chironomus nuditarsis Str. Rev. suisse Zool. 75: 538-549. 

 Hilsenhoff, W. L. 1966. The Biology of Chironomus plumosus ( Diptera : Chironomidae 



in Lake Winnebago, Wisconsin. Ann. ent. Soc. Am. 59: 465-473. 

 Klôtzli, A. M., F. Rômer und S. Rosin. 1971. Jahreszeitliche Grôssenvariation be 



Chironomus plumosus L. Rev. suisse Zool. 78: 587-603. 



