THE REACTIONS OF CERTAIN DERMESTIDAE TO 



LIGHT IN DIFFERENT PERIODS OF 



THEIR LIFE HISTORY 



J. E. WODSEDALEK 



The Zoological Laboratory, The University of Wisconsin 



PHOTOT ACTIO REACTIONS OF TROGODERMA TARS ALE, A 



MUSEUM PEST 



While working on the life history and habits of T. tarsale 1 

 I made some observations which suggested the idea that it 

 would be an advantage to know the exact phototactic reactions 

 of this beetle in the different periods of its life history. Careful 

 observations were made and it was noticed that the larvae 

 immediately after hatching evince a markedly negative reac- 

 tion to light by concealing themselves in any available shaded 

 areas. If placed near a window they at once begin to crawl 

 away from the light, and the reaction is even more pronounced 

 when the specimens are taken into a dark room and a strong 

 light is introduced at one end of the glass dish containing them. 

 This negative response persists throughout their larval life. 

 Before passing into the pupal stage their negative reaction is 

 especially pronounced. Thus, the pupae are almost invariably 

 found in dark places which afford them a favorable means of 

 protection. 



After metamorphosis, the adults, both male and female, retain 

 the negative phototaxis. As a rule the insects remain for some 

 time within the feeding material or cabinet in which they were 

 reared. A large number of newly emerged adults were taken 

 into a dark room and both sexes manifested a decidedly nega- 

 tive response to light of various intensities. During the sexual 

 excitement which follows a day or two later they still remain 

 negative. The female remains markedly so until her eggs are 

 safely deposited. Several hours later, or the day following the 

 egg-laying, the negative reaction is gradually inhibited until the 



1 Wodsedalek, J. E. "Life History and Habits of Trogoderma Tarsale, a Muse- 

 um Pest." Annals of the Entomological Society of America, vol. 5, No. 4. 



61 



