REVISI02ir OF LISTROCHELUS — SAYLOR 61 



ened tarsal segments of the latter are omitted from consideration. 

 Chlaenobia vexata Horn and C. unituberculata Bates have the male 

 tarsal segments only slightly more pilose than in normal male Phytalus, 

 while the segments themselves are not at all expanded. The front 

 tarsal segments are expanded in male C. latipes Bates, C. tumulosa, 

 etc., and not at all so (even though pilose below) in C. aequata Bates, 

 C. colimana Arrow, C. vexata Horn, etc. The situation here is exactly 

 comparable to that in Liogenys Guerin, wherein the tarsal segments 

 may vary in the male from normal size to twice or even three times 

 the normal width — this being therefore a sexual and specific variation 

 and not to be considered of generic importance. Thus the differences 

 between Chlaenobia tumulosa on the one hand and Phytalus chlaeno- 

 blana on the other are fully bridged over in the species C. vexata and 

 unituberculata, and the only alternative to suppressing Chlaenobia 

 entirely is to keep it as a subgenus of Phyllophaga; moreover, the 

 generic differences as set up between Phytalus and Chlaenobia hold 

 only in the male sex. 



In this connection I wish to quote a short paragraph from an 

 article by G. J. Arrow (of the British Museum of Natural History), 

 who has had wide and varied experience in scarab taxonomy for a 

 good many years. Mr. Arrow says (1938) in speaking of a scarab 

 genus: "Those who see advantage in the multiplication of generic 

 names may perhaps discover some diagnostic feature by which the 

 retention of one or both these names may be rendered possible. 

 Such attempts seem to me, however, to be only resisting an inevitable 

 process. As more and more species of any group become known, 

 previously apparent gaps in the series necessarily become filled, and 

 the disappearance of many genera is as natural as their erection at 

 an earlier date, when the known species were fewer." With this 

 statement I heartily concur. 



By treating Chlaenobia as a subgenus of Phyllophaga, most closely 

 allied to the subgenus Phytalus, and restricting to it those species 

 having closely cleft tarsal claws in both sexes, and the tarsal seg- 

 ments in the male more densely pilose than normal (with also widened 

 tarsal segments in some of the species), I believe the status and true 

 relationships of these subgenera will be better evidenced than by 

 using any other arrangement. 



ACKNOWLEDGMENTS 



It is a pleasure to acknowledge the assistance of many individuals 

 and institutions. Those contributing material for study or assisting 

 in other ways were: Dr. E. A. Chapin, the material in the U. S. 

 National Museum and the Casey Collection; G. J. Arrow, of the 



