266 Annals Entomological Society of America [Vol. XI, 



armed posterior femora, unarmed proiaotum and tibiae and well 

 developed scent gland orifices. 



The species have been described singly with only meager 

 comparative notes, with the result tha't superficial instead 

 of fundamental characters have usually been employed to 

 distinguish them. A synopsis of the genus based on coloration 

 and wing characters has been published by Barber il911). 

 Owing to numerous variations, especially in A. eurinns and 

 A. conspersus, the present writer has been compelled to rely on 

 genitalia for the separation of these two species and their 

 relatives. Fortunately, this method is easy to apply as Alydiis 

 has the claspers of the male exposed instead of covered. They 

 are described in the Key as seen from the caudal aspect ; no 

 dissection is necessary. 



KEY TO SPECIES OF ALYDUS. 

 a. Venation of the membrane simple, veins not irregular and only sligiitiy 

 anastomosing; claspers of male when arcuate not toothed near ape.K; 

 posterior femora not with pale annulus. 



b. Pronotum with lateral angles blunt, and sides and lateral margins 

 not distinctly paler than the disc. 



c. Claspers of male with caudomesal margins subparallel, 



caudal aspect narrow (Fig. 2); female of pluto with 



lateral plates of hypopygium terminating in a tumid 



finger-like process (Fig. Ij; sixth ventral segment 



with a distinct median carina; mainly mountain species. 



d. Antennse with fourth segment shorter than 



second and third together, third subequal to 



second; body black, not densely pilose; 



(genitalia, figs. 1,2) pinto Uhl. 



(Id. Antennas with fourth segment more than one- 

 third longer than_ second and third together, 

 third shorter than second; body variegated 

 with fuscous, densely pilose; (o"^ claspers, 



fig. 3) tomentosus n. sp. 



cc. Claspers of male not with caudo-mesal margins parallel; 

 lateral plates of female hypopygium flat, not tumid at 

 tip, sixth ventral segment with carina short, indis- 

 tinct or wanting; widely distributed species. 



d. Claspers of male twisted, not arcuate (Fig. o); 

 lateral plates of female hypopygium acute 

 at apex (Fig. 4); pronotum usually black; 



membrane infuscate eurinus Say. 



dd. Claspers of male arcuate, divaricate at.baseand 

 convergent at tip (Fig. 8); lateral plates of 

 female hypopygium broadly rounded at apex 

 (Fig. 7); pronotum usually with posterior two- 

 thirds fulvous; membrane often spotted 



conspersus Montd. 

 Ijb. Pronotum with lateral angles acute and lateral margins pale; 

 claspers of male with lateral expansion and acuminate tip 

 (Fig. 10); lateral plates of female hypopygium bluntly rounded, 



approximate at apex (Fig. 9) pilosulus H.-S. 



aa. Venation of membrane, or at least costal third, irregular with anastom- 

 osing veins; posterior femora with pale annulus near apex; claspers of 

 male elongate, arcuate, with an enlarged stout mesal tooth near apex 

 (Fig. 6) sciitellatus Van D. 



