570 INSECTA. 



Sometimes the ninth and tenth joints of the antennae, the length 

 of which, at most, is equal to that of the head and thorax, are hardly 

 larger than the preceding ones; the eleventh or last is alone much 

 thicker, nearly spherical, and with an acicular point at the end. 



BiTHYNUS, Leach. 



Where the second joint of the antennae is much thicker than the 

 first, and dilated on the inner side in the manner of a tooth(l). 



Arcopagus, Leach. 



Where, on the contrary, the second joint of the antennae is much 

 more slender than the first, and where the latter is even sometimes 

 dilated(2). 



There the maxillary palpi are shorter than the head and thorax 

 taken together^ the fourth joint at least is short or but slightly elon- 

 gated, and ovoid or triangular. 



Ctenistes, Reich. 



These Insects are very distinct from all others of the same family, 

 in the three last joints of their maxillary palpi, on the outer side of 

 which we observe a point or tooth with a terminal seta; the second 

 is very long, arcuated, and inflated and rounded at the end; the two 

 following ones are almost globular. The last joint of the antennae 

 is much larger than the preceding ones, and somewhat oval. The 

 thorax forms an elongated and truncated cone(3). 



Dryaxis, Leach. — Euplectus, Tychus^ Ejusd. 



Where no such characters are presented by the maxillary palpi; 

 their last joint is elongated and conical or securiform. The thorax 

 is short, hardly longer than wide, and rounded(4). 



In the last of the Pselaphii we observe this peculiarity — their an- 

 tennae consist of but six joints, or even one. They form the genus. 



Claviger, 



Claviger proper, 

 Where the antennae consist of six distinct joints. 



(1) Pa. securiger, ejusd. See I.each, Zool. Miscell., Ill, page 80, 82, 83. 



(2) Ps. glabricollis, Reich ; ejusd., Ps. clavicomis; Leach, lb., 80, 83, 84. 



(3) Reich., Monog, p. 75, et seq. 



(4) See Leach, Zool. Misc. The form of the last joint of the maxillary palpi, 

 as well as the relative proportions of those of the antennse, may offer good cha- 

 racters for division, but they do not appear to me of sufficient importance to 

 designate generic sections. See the article Pselaphiens of the Encyclopedic Me- 

 thodique. 



