20 NEOTROPICAL PSELAPHIDAE 



This diversity is demonstrated by the plates and in the descriptions which 

 follow, and is not confined to a single subfamily, tribe or genus but extends 

 through the entire family. In many cases special antennal modification is re- 

 stricted to one sex, usually the male ; in many cases both sexes have the anten- 

 nae modified. 



The method of articulation of the pselaphid antenna is notable, and has 

 been previously discussed by Casey, Raffray and other students but has not 

 been sufficiently appreciated by coleopterists as a whole. Pselaphidae have the 

 first antennomere flexed dorsad to articulate on the upper wall of the antennal 

 acetabulum, or where the acetabulum is functionally obsolete (as in the spe- 

 cies with contiguous antennae mounted on a median antennal tubercle) then 

 this segment is articulated on the ventral face of the tubercle. Hence the 

 pselaphid antennal articulation is restrictive as contrasted to the articulation 

 of staphylinids. The Staphylinidae show some variation, but quite generally 

 have antennae which do not articulate on the upper wall of the acetabulum 

 and do not have such pronounced antennal tubercles. This may be a prophetic 

 difference, that is, the pselaphid antennal-articulation plan is suggested here 

 and there in the staphylinids — giving yet another hint as to original stock of 

 the pselaphids. 



The vertex of the pselaphid head capsule usually bears a pair of vertexal 

 foveae. These foveae are very characteristic of the entire family. They repre- 

 sent invaginations of the integument, and in slide mounts these foveae are 

 seen to have their floors attached to the arms of the V-shaped supratentorium 

 of the endoskeleton, the supratentoria continuing ventrad where the two oblique 

 arms unite ventro-posteriorly to attach to the floor of the median gular fovea. 

 This latter usually is present as an invagination of the integument near the 

 demarcation of the ventral surface of the head proper and the cervicum. 

 Rarely the arms of the supratentorium attach to the ventral surface of the 

 head without forming the gular fovea ; at times the single gular fovea bifurcates 

 internally to form two ventrally continuous foveae; in still other cases there 

 are two entirely separate but approximate gular foveae, each attaching to 

 one arm of the supratentorium. 



The vertexal foveae are rarely absent {Adranes, Nisaxis), although they 

 may be very minute {Fustiger, Barrojuba, Trimiomelba, Ceophyllus) . In some 

 genera these foveae are highly specialized. Thus in Pselaphus they are drawn 

 forward to produce two voluminous subfrontal cavities, the orifices of which 

 are so far anteriad of the supratentorial anchorage that they may be over- 

 looked at first. It is as though in Pselaphus the forward attenuation of the 

 antennal tubercle had pulled the head capsule integument anteriorly between 

 the eyes while, the floor of the foveae being held by the supratentorium, the 

 walls were consequently stretched abnormally. The vertexal foveae as a gen- 

 eral rule are normally sized and placed but their walls may be wholly nude 

 or densely pubescent. In some genera {Euplectus, Batrisodes, Hamotus) the 

 foveae may be both nude and pubescent within the same genus, but this is not 

 a common condition. Rarely the foveae are wholly obscured by dense cephalic 



