358 Trans. Acad. Set. of St. Louis. 



body. The prosternum is short and not much produced in 

 the middle under the coxae ; its anterior margin is broadly 

 and distinctly sinuate, except in Platyprosopus and Hyptioma^ 

 where it becomes truncate. The membrane thus exposed in 

 the sinuation is partially covered by a complex arrangement 

 of extruded corneous plates, the central large and broadly 

 arcuate at tip, the lateral small and more extensile. These 

 plates are undoubtedly connected in some way with the un- 

 usual flexility of the head ; they appear to be wanting in the 

 Paederini, where the exposed piece, when present at all, isi 

 much shorter and membranous or coriaceous in texture. The 

 tarsi are remarkably uniform in structure and present nothing 

 unusual ; the anterior are undilated as a rule but become strong- 

 ly dilated and densely pubescent beneath in certain genera, 

 notably Platyprosopus, where they are also eccentric as in 

 Pinophilus, in LeptoUnus and NotoUnus and one or two others 

 of the Xantholini, in Diochus and the Othii. 



The sexual characters at the ventral apex are singularly in- 

 conspicuous when we compare the tribe with many others, 

 such as the Paederini, and the most notable sexual characters 

 generally apply to the female and not the male. In the male 

 of ISFematolinus and HesperoUnus, for example, the sixth 

 ventral is broadly rounded at tip, but in the female is either 

 acutely angulate or produced in a slender spine, which, in 

 parous and one or two other species, extends well behind the 

 extreme tip of the abdomen. The female characters of Lep- 

 tacinus are also peculiar as noted below. In the Othii, how- 

 ever, the male frequently has the sixth segment more or less 

 evidently sinuate at tip, and it is an invariable rule that the 

 apex of the sixth ventral is less arcuate or less produced in 

 the male than in the female, even when the actual diiference 

 of curvature is very slight, as in Nudobius and Xantholinus. 



It is convenient to divide the tribe, as represented by the 

 material that happens to be in my cabinet, into seven sub- 

 tribal groups distinguished by the following characters : — 



Prosternum emarginate anteriorly, the emarginalion partially filled by aa 



apparently extrusive rounded corneous plate 8 



Prosternum transversely truncate anteriorly, without extrusive corneous 



