3 2 
Psyche 
[March 
they are also quite distinct from one another, and it would be difficult 
to derive them from a common stem. The kinds of adaptive struc- 
tures occurring in the two groups are entirely different. The glandu- 
lar structures in Gnostus consist of trichomes on the pronotum, 
while those of Fabrasia consist of scattered pores on the 1 elytra and 
a brush of hairs on either side of the distal articulation of the hind 
femur. The legs of Gnostus may be flattened and expanded like 
those of certain Paussidae, while the species of Fabrasia have pecul- 
iarly enlarged and club-like femora, which to our knowledge are 
unknown in any other beetle group. Characters of the head, antennae, 
prosternum, abdomen, and genitalia show similar differences. We 
think that the two genera were probably independently derived from 
Ptinus- like ancestors, perhaps early in the evolution of the family. 
Since most of the ant host species appear to nest in woody habitats, 
the beetles may have evolved from subcortical scavengers which had 
originally been derived from wood-boring ancestors (Crowson, 
1955). It appears reasonable to retain the subfamilies Gnostinae 
and Fabrasiinae for the present, but in a revision of the family they 
may well be reduced to tribal rank within the Ptininae. 
In 1962, Costa Lima described another apparently myrmecophilous 
ptinid, Plaumanniola sanctaecatharinae, which he made the type of 
another subfamily. The type of this species has been examined, and 
it was found to belong to the family Scydmaenidae (Lawrence and 
Reichardt, 1966). 
Gnostus Westwood 
(Figs. 1 — 5, 13 — 15) 
Gnostus Westwood, 1855, Trans. Ent. Soc. London, (2)3: 90. (type species: 
Gnostus formicicola Westwood, by monotypy). 
description: Form elongate, convex; vestiture of short, suberect, 
sparsely distributed, fine hairs; surface shiny. Head strongly de- 
clined, only partly visible from above; vertex concave, forming a 
broad transverse impression, joined laterally on each side to a deep 
and narrow, oblique groove extending to the eye below; eyes lateral, 
relatively small, elongate and carinate ; antennal fossae relatively deep, 
located well above the eyes, separated by a sharp median carina; 
clypeus subtriangular, almost as long as wide, strongly tumid, and 
emarginate at apex; labrum inflexed and concave. Antennae (Fig. 5) 
3-segmented, relatively short (not reaching base of pronotum) ; seg- 
ment I elongate, slightly curved, expanded towards apex; II about 
half as long as I, inserted beneath the latter, terminal segment almost 
twice as long as I and II together, expanded ventrally at middle 
and truncate apically, the tip excavate and filled with short hairs. 
