MONOPLATUS. 5 



peet to find in the male ; but there is this peculiar characteristic in 

 the female, that its posterior tibiae are armed with series of tooth- 

 like prominences, which are not only not so clearly developed, but 

 are hardly traceable at all in the males. 



To a greater or less extent in most of the Ralticce proper and Lon- 

 gitarsi, the enlargement of the basal joint of the tarsus (Front, fig. 2a) 

 holds good as a sexual characteristic. Sometimes this is only faintly 

 expressed; thus in the European Longitarsi it may be traced di- 

 stinctly, although comparatively obsolete. Mr. Wollaston finds the 

 same sexual contrast in a Canarian species (Longitarsus Kleiniiperda , 

 Woll.). In examples which I have received from him, the antical 

 tibia? (as well as the anterior tarsi) are dilated in the males ; but the 

 basal joint of the tarsi, although much more prominent than in Eu- 

 ropean species, is considerably less developed than in the group before 

 us — Monoplatus. Thus we find that in this instance at least, the 

 sexual distinctions which obtain in a part of the same subfamily of 

 insects, and which are apparent in the temperate zones, become more 

 pronounced in the subtropical, and attain their maximum of difference 

 in the representative group which is found in the regions nearer to 

 the equator. 



1. Monoplatus nigripes. (Tab. I. fig. 1.) 



M. ( 2 ) oblongo-ovalis, subcylindricus, glaber, niger ; capite brevi, 

 depresso, antice inter ocidos subtiliter foveolato, impunctato, 

 jiavo-ferrugineo ; thorace quadrato, antice emarginato, ad basin 

 transverse canaliculato, impunctato, jiavo, nitido ; elytris robustis, 

 punctato-striatis, ad apicem subattenuatis, nigris, nitidis; antennis 

 filiformibus, nigro-fuscis ; pedibus nigris, femoribus anticis fusco 

 suffusis. 



2 Long. corp. 3 lin., lat. Ik lin. 



Oblong-ovate, robust, subcylindrieal, impubescent, shining, black. 

 Head short, depressed, not produced in front ; the eyes are large, 

 prominent, and black, situated at the base of the head, the distance 

 between them being not greater than the diameter of either ; above 

 the base of the antennae is an irregular medial depression ; the sur- 

 face is impunctate, shining, and rufo -ferruginous. Thorax broader 

 than the head, transverse, and rectangular ; the anterior margin is 

 distinctly and circularly emarginate ; the anterior angles are sub- 

 acute and depressed ; the sides marginate, especially anteriorly ; the 

 basal angles are slightly truncate : parallel to the margin of the base 

 is a well-defined thread-like fovea, which does not extend to the 

 sides, but is abruptly and at right angles deflected to the base ; 

 this fovea is in its course slightly subsinuate ; the surface is im- 



