BEMBIDIIN/E 191 



i 



fication in elytral striation, erroneously assuming, however, that 

 this was due to simple variability; the large series at hand show 

 that this is not by any means probable. Liebecki Hayw., evidently 

 belongs also to this extensive xanthopus section, but appears to be 

 larger, stouter and with more transverse prothorax than any known 

 to me; it is said by Mr. Hayward to be 2-2.5 mm - m length and 

 occurs in Texas; the elytra are said to be gradually pallescent 

 posteriorly. 



Tachys Steph. 



Polyderis Mots, (pars.) 



This remarkably isolated genus may always be distinguished at 

 a glance from any species of Tachyura by the subdepressed form of 

 the body, thinner integument and usually less polished surface, the 

 elytra being frequently opalescent because of the minute sculpture. 

 In fact the entire habitus of the two genera is so different that it 

 seems strange they should have ever been closely associated; this 

 was thoroughly recognized by those usually careful observers Mot- 

 schulsky and Chaudoir, but I do not quite understand why the 

 latter author in describing Barytachys should have failed to recog- 

 nize its identity with Tachyura Mots.; this applies also to Mr. 

 Bates in his treatment of Tachys in the "Biologia." 



Tachys differs from Tachyura, not only in the characters stated 

 above, but in possessing on the surface of the mentum two deep, 

 circular and very abruptly defined foramina, similar to those of 

 Pericompsus but smaller in size and wanting in all other genera of 

 the Tachys group excepting Paratachys. It differs also in the very 

 shallow sutural stria, but resembles it in having but few .striae and 

 in the broad interruption of the eighth stria; the latter, besides 

 being even more widely interrupted than in Tachyura, is more ir- 

 regular and frequently in part altogether obsolete, leaving merely 

 a row of setigerous foveae. The maxillary palpi are slender as a 

 rule, the second joint of the labial stout, the last segment of the 

 outer maxillary lobe very slender and the mentum tooth small and 

 sharply triangular. Our numerous species are assignable to the 

 three following subgeneric groups : 



Front broadly bisulcate: eyes well developed; antennae long; recurved 

 apical part of the sutural stria long 2 



