All the genera of the staphylinid subfamily Trichopseniinae, except for one which was revised earlier, are redescribed and illustrated, and a key differentiating all the genera is provided. Six new genera are described: PRORHINOPSENIUS, CONGOPSENIVS, PARRHINOPSENIUS, SEEVERSIA, SCHEDOLIMULUS, and PHORILIMULUS. All previously described species of the genera herein revised are redescribed, and new characters are illustrated except for the genera Trichopsenius and Xenistusa, the revision for which is postponed until more new material becomes available. Six new species are described: Congopsenius bouilloni (Congo Republic) ; Parrhinopsenius kemneri (Sarawak), Seeversia emersoni (Sarawak), Seeversia sarawakensis (Sarawak), Schedolimulus pumilio (Sarawak), and Phorilimulus minutus (Sarawak). Many new geographic and host data of the species are presented.
The integumentary glands are described in 4 genera: Trichopsenius, Xenistusa, and Schizelythron showing various degrees of physogastry, and in the limuloid Congopsenius. Glands present in all these genera are believed to be ancient structures and are called primary glands. These primary glands are the maxillary, the articular, the postbuccal, and hypodermal glandular cells of 2 types. Type 1 cells open at the surface of sclerites subject to friction, and type 2 cells are situated under the uncovered part of the sclerites. In Xenistusa and Trichopsenius, the type 1 cells are unusually abundant in the abdominal sclerites and are situated principally at their anterior corners. These cells appear also very numerous and active in the elytra of Schizelythron. Besides the primary glands, both Xenistusa and Schizelythron possess secondary glandular structures. In Xenistusa, these unique glands consist of a pronotal gland and numerous type 4 glandular cells which are widely distributed but apparently more numerous on both sides of the abdomen. In Schizelythron the secondary glandular structures consist of a labral gland, an antebuccal gland, and glandular surfaces between tergites II and III and between tergite III and sternite III.
Hypertrophy of type 1 cells and the development of secondary glands are believed to be adaptations which may act during host-guest interactions.
These results are compared with results of similar studies on free-living and termitophilous aleocharines. The primary glandular systems of the aleocharines and of the Trichopseniinae are similar, but both subfamilies possess some unique glandular structures: the postbuccal gland in the Trichopseniinae and the defense gland and the post pleural glands in the aleocharines. Glands of possible significance in termite–termitophile interactions are most numerous in the physogastric genera of both subfamilies.
The relationships between the genera and species were analyzed numerically and a phenogram was constructed. This analysis indicates that a limuloid group of genera evolved very early and that further specialization of these genera occurred within the context of the generic differentiation of the termite hosts. Two physogastric groups probably also evolved early in the phylogeny of the termites as these 2 groups are found in different subfamilies of the Rhinotermitidae. There is some evidence that the physogastric genera evolved a little later than the limuloid genera as they are not known from the more primitive rhinotermitid genera.
Evidence from the study of the external and internal morphology suggests that the common ancestor of the limuloid and physogastric line was limuloid in form.
All species are host specific at the species level and a summary of the host information is presented. Host records outside the family Rhinotermitidae are presently interpreted as artifacts of the collection process. If these host records should be verified, host transfers would have to be postulated.
