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Notes on Xyleborus dispar, Fabr. By Dr. T. A. Chapman. 



We had the pleasure of studying a colony of these 

 beetles at Moncayo, and were able fully to accept all that 

 we have been told about them by Eatzeburg, Ormerod, 

 Blandford, etc. Perhaps the best account of them, in- 

 cluding as it does their congeners and relatives, is that of 

 H. G. Hubbard in Bulletin No. 7, U. S. Dept. Agr. 1897. 



We found that the males never left the stumps in which 

 they are bred, being wingless, and having jaws of little 

 use except for tearing through any little overgrowth of 

 fungus in the burrows. Their degeneration in size and 

 form as compared with the females is, of course, associated 

 with this change of habit. 



^17 



Fia. 1. — Relative size and form 

 of jaws of i and 9 X. dispar. 

 Tlie process to the riglit is a portion 

 of tendon. 



Fig. 2. — Relative width 

 of head of i and 9 X. dispar. 

 The greater anterior posterior 

 diameter of that of the 9 is 

 due to the protrusion of the 

 head, as much as to larger 

 size. 



The relative size of the head of the ^ and $ is 

 lineally as 3 to 2, the width of the male head being O'G 

 mm. and of the female O'D mm. — making in volume a 

 ratio of 27 to 8, or about 3i to 1. 



The jaws also differ much in size. The greatest length 

 of the male jaw is 021 mm. and of the female 0-33 mm. 

 Each has the double tip as in the larval jaw, but in the 

 female this is obviously supplemented by a straight 

 margin, which is very slightly marked in the male ; there 

 is a still greater difference in the chitinization, the male 

 jaw being brown and translucent, that of the female dense 

 black. 



