1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 503 



acters which would lead to fusca in Dr. Horn's table of species 24-32 

 on page 238 of his Revision : 



Clypeus distinctly emarginate, the angles rounded. 



Ventral ridge of male small, well detiueil, strongly arcuate and overhanging the 

 ends at the extreme margin of the penultimate segment, and somewhat over- 

 hanging the penultimate segment arcuala 



Ventral ridge of male small, well defiued, not overhanging, the ends, and indeed 

 the entire ridge, near the middle of the segment insverata 



Ventral ridge of male longer, decidedly arcuate, but not so much as before, over- 

 hanging posteriorly for its full length, the ends at some distance from the pos- 

 terior margin of the penultimate segment dubia 



Ventral ridge of male still longer, slightly curved, the ends overhanging poste- 

 riorly ; centrally the ridge is declivous, but not overhanging behiud fiisca 



Ventral ridge of male elevated, nearly straight, not overhanging, scarcely de- 

 clivous at ends ; at center the posterior declivity nearly as gentle as the ante- 

 rior g nitidis 



Ventral ridge of male not elevated, rigidly straight, and behind it an abrupt 



depression of the segment ulkei 



Clypeus feebly emarginate, nearly quadrate, the angles not rounded quadrata 



By this table the males may be distinguished without much trouble. 

 The females are not so easily separated, yet may be in most cases asso- 

 ciated with the males. 



32. L. arcuata Smith. 



This species, as a whole, averages rather smaller than either of the 

 others. From dubia it does not, in the female, differ at all in superficial 

 characters, every effort to discover any feature whereby specimens of 

 this sex might be distinguished from each other kaviug failed. As the 

 genital structure is so distinct, this is somewhat surprising, and possibly 

 the true character has been still overlooked. 



The primary characters of the female are much as in dubia, and yet 

 obviously different. The pubic process while divided at tip, much as 

 in dubia, is only about one-half as long and does uot divide the upper 

 plates as in that species. It resembles the upper part of the dubia 

 structure set upon the superior plates ; these latter are large and nearly 

 quadrate, in marked contrast with the narrow linear structures of dubia. 

 The inferior plates differ as markedly, as can be readily seen by a com- 

 parison of the figures. 



The males also in habitus do not differ from the allied species, except 

 in ventral characters, but these are obvious and easily recognized. 

 The ridge in this species is very much curved, very much overhanging, 

 the ends reaching the apical margin of the segment, while the arch, 

 combined with the depression of the last segment, forms a perfect 

 ovah 



In this species the space included by the arch of the ridge is smooth. 



The species seems rather more southern than some of the others. It 

 is practically the only form taken at Washington, many thousands 

 being taken, while only one specimen of the other forms was discovered. 

 Other localities are New York, New Jersey, central Missouri, Iowa, 



