594 Mr. G. J. Arrow on 



tibiae and tarsi with numerous ones. Wings hyaline : veins 

 yellow ; the first vein from the discal cell bulges at the base 

 into the first posterior cell, which is open at border ; the 

 fourth is also open, but the last [jart of its upper vein from 

 the transverse vein enclosing the discal cell turns so sharply 

 downwards that it almost closes the cell, leaving only a narrow 

 opening at border. Halteres yellow. 



[To be continued.] 



LXV. — A Synoptical Revision of the Coleopterous Genus 

 Hexodon (Dynastinai). By Gilbert J. Arrow. 



(Published by permission of tlie Trustees of the British Museum.) 



The genus Hexodon forms a very homogeneous and peculiar 

 group of species confined to Madagascar and owing its chief 

 distinctive feature to the loss of the wings, a highly ex- 

 ceptional phenomenon in the Dynastinae, but evidently here 

 of very ancient date. It has been accompanied, as in 

 apterous Coleoptera of various other groups, by the develop- 

 ment of lateral folds to the elytra and the reduction of the 

 shoulder prominences, aud the latter feature has been 

 balanced in Hexodon by the horizontal development of the 

 lateral folds and the production of secondary or false 

 shoulders. 



A further peculiarity is found in the structure of the 

 antennal club, the first joint of which is drawn out in such 

 a way that the point of articulation of the penultimate joint 

 is removed to near its middle. 



The sexual characteristics of the genus, which have not 

 been noticed, although strongly marked, arc interesting as 

 combining two opposite tendencies exhibited in the Dynas- 

 tinae. In a large part of that subfamily the males have the 

 front claws unsymmctrical and the inner one enlarged and 

 distorted or toothed. This is almost always accompanied by 

 a considerable shortening and tiiickening of the front tarsus. 

 In another great division all the tarsi, but especially the 

 front ones, are elongated in the males, the claws remaining 

 simple and symmetrical. In Hexodon the inner front claw 

 is thickened and distorted, but at the same time there is a 

 great elongation of all the tarsi as in the second division. 

 The pygidium is vertical in the male and oblique and more 

 exposed in the female. 



The combination of features elsewhere distinctive of 



