COLOR CHANGES IN THE RHINOCEROS BEETLE, 

 DYNASTES TITYRUS 



E. A. ANDREWS 



From the Zoological Laboratory, Johns Hopkins University 



FOUR FIGURES 



PART 1 



The ^rhinoceros' or 'cow' beetle of the Southern United States 

 is noted not only for its great size but for the marked differences 

 between the males and the females. In the male (fig. 1), the 

 head bears a long horn pointing forward and overhung by a 

 still longer horn from the thorax and there are two smaller 

 horns one on each side of the large thoracic horn. In the female 

 (fig. 2) there is but a slight suggestion of a horn on the head and 

 none at all on the thorax. The spots on the wing cases of the 

 female are also smaller than those of the male. 



These horns of the male have been cited as good examples of 

 so called secondary sexual characters, the use of which however 

 is entirely problematical. 



Some of these beetles found in a dead stump in the Eastern 

 Shore of Maryland were kept in captivity in glass aquaria with 

 moist decayed wood and pieces of apple for more than a month, 

 but no evidence of use was found for these secondary sexual 

 characters though it was noted that the male in throwing back 

 the head may oppose the horn on the head to that on the thorax 

 with force sufficient to suspend its weight from one's finger. 

 The remarkable tuft of setae, like a hair-brush, on the under 

 side of the thoracic horn raises the question whether it may not 

 be sensory and aid the beetle in estimating the size, etc., of ob- 

 jects clasped between the two horns and in the literature is 

 found the suggestion that the male holds the female. How- 

 ever, watching males and females showed that while early in 

 June the male followed the female for days and seized her with 



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