144 Journal New York Entomological Society. [Vol. viii. 



the hypomera are merely flat or concave, without trace of an enclosed 

 antennal fossa, but in Trogoderma the fossa appears in one of its prim- 

 itive stages, and may be conceived to be the result of retractility of 

 the anterior femora. The crural fossae are deep and denned anteriorly 

 by a strongly elevated acute cariniform line, extending obliquely to the 

 hind angles of the prothorax, and forming the posterior boundary of 

 the hypomeral concavity. To suggest that this latter concavity has 

 not been evolved primarily as a shelter for the antenna; as in An- 

 t/iremis, for example, it may be observed that it is equally large and 

 well formed in both sexes, although the antenna; differ sexually to a 

 great degree, and it is only in the male that it is in any way com- 

 pletely utilized or compactly filled by that organ ; in the female, 

 where the antenna; are comparatively very feebly developed, these 

 organs lie in repose along the bottom of the concavity, which is much 

 too large to form a secure shelter. In Trogoderma the fossa occupies 

 the entire length of the prothorax, but in Cryptorhopalum while hav- 

 ing a general form which undoubtedly betrays a development from 

 that of Trogoderma, it has become smaller and forms a secure shelter 

 for the antenna;, these having become similar in the sexes and assum- 

 ing a form so radically different from those of Trogoderma that it is 

 difficult to trace any philogenetic relationship, and in Thaumatoglossa, 

 the modification is carried still further, the two closely connected 

 club-joints of Cryptorhopalum becoming a single very large joint. 

 Acolpus appears to be a very satisfactory intermediate between the 

 non-fossate genera and Trogoderma, and it is possible that more care- 

 ful observation may there show the antennal fossa in a still more in- 

 cipient stage of formation. The American genera may be defined as 

 follows : — 



Basal joint of the hind tarsi very short, much shorter than the second ; antennal fossa 

 not defined ; legs free, the hind femora retractile as usual 2 



Basal joint elongate, generally but little shorter than the next two combined ; antenna? 

 1 1 -j oin ted in both sexes 3 



2 — Antennae n-jointed in both sexes, the two basal joints of the male club short 

 and transverse, the last greatly elongated ; mesosternum between the coxae longer 

 than wide, not sulcate, the anterior coxae narrowly separated ; metacoxal lamina 

 greatly elongated internally AttagenilS 



Antennae 10-jointed in the male, 11-jointed in the female, the two basal joints of the 

 male club much elongated and the last joint relatively much less so ; meso- 

 sternum between the coxae very narrow and elongate, not sulcate, the prosternal 

 process extremely narrow ; metacoxal lamina as in Atlagenus, the epipleurae less 

 inflexed and less strongly defined ; body with denser and more variegated pubes- 

 cence Novelsis 



