a few Melolonthine Coleoptera. 25 



of the hind tarsus is slightly longer than the following one, 

 and the claws are strongly curved and toothed in the middle. 



The male is easily recognizable by the exceptional length 

 of the antennal club, and another slight but important diffe- 

 rence is found in the claws, in which the tooth is placed 

 nearer to the tip in the male than in the female. 



I have used the generic name Rhizotrogus because it is the 

 oldest of the various names in use for the immense and 

 almost world-wide series of species to which these three 

 insects belong, although that name is generally restricted to 

 species from the Palsearctic region. Tiie classification of 

 these insects is very largely a geographical one at present, 

 and species from the Oriental region are referred to Holo- 

 trichia, those from America to Lachnosterna, while those 

 from the Palsearctic, African, and Madagascan areas have 

 been distributed under very numerous names, some of which 

 are no doubt well justified, but the maintenance of others 

 must necessitate the introduction of a very large number of 

 fresh generic names for the forms yet undescribed and con- 

 forming to none of the feebly differentiated diagnoses formu- 

 lated by Brenske, Reitter, and Kolbe. The handling of the 

 extremely difficult generic problem by artificially limited 

 geographical groups enables genera to be defined in terms 

 which are found inapplicable when entire natural groups 

 come to be investigated. Reitter, for instance, studying 

 Palsearctic forms, has divided the genera of the present group 

 into two sections according to the situation of the tooth upon 

 the claws before or behind their middle, one section being- 

 represented by Rhizotrogus and the other by Holotrichia. 

 As thus defined, the male of the species last described would 

 be referred to the Holotrichia section and the female to the 

 Rhizotrogus section. The many forms in which the tooth is 

 placed precisely in the middle completely bridge the two 

 groups and render their generic separation impossible. 

 Pending a general revision, therefore, it seems to me best to 

 accept only those genera which appear to be exactly defined, 

 and to regard as a single genus the great mass of species at 

 present called Rhizotrogus, Holotrichia, or Lachnosterna. 



Two species, not closely related, were described by Water- 

 house from the island of Rodriguez under the name of 

 Lachnosterna. L. rodriguezi, Wat., is a very peculiar insect 

 belonging to no known genus. Unfortunately the two 

 specimens are in an extiemely imperfect state, so that it is 

 not yet possible to state all its distinctive features ; but, 



