Fossatyloides Klopfstein et al. 2011

Klopfstein, Seraina, 2014, Revision of the Western Palaearctic Diplazontinae (Hymenoptera, Ichneumonidae), Zootaxa 3801 (1), pp. 1-143 : 56-57

Fossatyloides Klopfstein et al. 2011

Type species. Bassus gracilentus Holmgren 1858

Diagnosis. Males of this genus have unique modifications of the antenna, with a deep pit adjacent to the linear, narrow tyloid which is common in the genus group. Females are more difficult to place, but the petiolar area of the propodeum is enclosed by several parallel carinae, which is a unique feature. Some of the carinae can, however, be partly reduced in some specimens, and I thus include a short-cut in the Homotropus key to the present genus. The diagnostic deep pit adjacent to the narrow, linear tyloid has also been described as a bulbous swelling ( Dasch 1964a), but this interpretation of the structure could not be confirmed. Even when antennae of a male caught in alcohol were exposed to increasing pressure ( Klopfstein et al. 2010b), the pit remained invaginated. It can thus be assumed that this structure is rather a pit than an outward swelling also in the living wasp.

Face coriaceous and matt, without vertical impressions, in females black, in males yellow. Clypeus with apical margin thin, impressed along margin, resulting in the central area being convex. Antenna with 19–21 flagellomeres, apical flagellomeres much longer than wide, in males with linear, narrow tyloids and adjacent pits, without long setae. Mesoscutum without notauli; entirely smooth and shining, yellow shoulder marks large, their inner corners usually extended into two parallel lines on mesoscutum; mesopleuron with some irregular sculpture on lower part; epicnemial carina complete ventrally. Propodeum with longitudinal carinae present, but basal area only indicated by weak carinae, with petiolar enclosed by several concentric, arcuate carinae; propodeal spiracle inconspicuous; scutellum only carinate basally. Fore wing areolet present, but vein 3rs-m often unpigmented; hind wing with 2 basal hamuli. Hind tibia orange. Female metasoma evenly tapered from fourth segment to apex, hind margins of the tergites convex, tergites without transverse impressions. First tergite without median dorsal carinae. Second and third tergites with spiracles dorsal, above lateral folds. Metasoma black, marked with orange on tergites 2 to 4 or 5. Ovipositor sheaths 0.3 times as long as hind tibia, tapered and diagonally truncate apically, thus with the extreme tip of the ovipositor exposed; with inconspicuous setae ventrally and apically. Male with tergites 9 and 10 as distinct sclerites, sternite 9 about two times wider than long, emarginated apically, thus forming two lobes, their outer corners rounded.

Phylogeny. This genus was erected because F. gracilentus clustered together with a species of a tropical genus, Schachticraspedon , and outside the genus Homotropus as newly circumscribed in a molecular and combined molecular-morphological phylogeny ( Klopfstein et al. 2011). For a more detailed picture of its origin, additional tropical taxa would need to be sampled, especially from the genera Schachticraspedon and Syrphidepulo .

Distribution. Holarctic. Besides the Holarctic Fossatyloides gracilentus , this genus also includes the Nearctic Fossatyloides sicarius Dasch.

Biology. Nothing is known about the biology of this genus.