Palpostilpnus Aubert, 1961

Reshchikov, Alexey, Santos, Bernardo F., Liu, Jing-Xian & Barthélémy, Christophe, 2019, Review of Palpostilpnus Aubert (Hymenoptera, Ichneumonidae, Phygadeuontinae), with the description of ten new species, European Journal of Taxonomy 582, pp. 1-63 : 9-10

Palpostilpnus Aubert, 1961

Palpostilpnus Aubert, 1961: 56–58 (type species: Townostilpnus (Palpostilpnus) palpator Aubert, 1961 ; designated in Townes 1970).

Expanded diagnosis

Head short and depressed; gena narrow, in frontal view not bulging behind eyes. Mandible small, subbasally swollen, with basal, transverse groove. Malar sulcus indistinct. Maxillary palp reaching base of hind coxa or almost so. Antenna slightly shorter to distinctly longer than body, strongly enlarged and somewhat flattened at midlength, ventral face distinctly flattened, lighter in colour. Occipital carina reaching base of mandible. Mesosoma stout, short to moderately long, but always somewhat obliquely sloped. Sternaulus shallow, complete or distinct only on anterior 0.5. Episternal scrobe deep or shallow. Hind tibia gradually and distinctly enlarged towards apex. Hind tarsal claws very small. Areola fused with petiolar area; median longitudinal carinae, when present, parallel. Forewing crossvein 2m-cu inclivous, with one bulla. T1 1.5–2.5 times as long as apically broad, without median dorsal carina. Ovipositor very slender, needle-like, as long as 0.20–3.50 of hind basitarsus.

Remarks

The most readily recognizable diagnostic feature of Palpostilpnus is the very long maxillary palp, reaching the base of the hind coxa. Although very characteristic, this trait is not unique of Palpostilpnus : most of the genera placed in Townes’ subtribe Chiroticina show somewhat elongated palpi. Palpostilpnus can be readily differentiated from these taxa by having the mandible small and slender, with a basal transverse groove, and a very slender, needle-like ovipositor. Since P. rufinator ( Aubert, 1961) stat. rev. also shows all these character states, and bears much more morphological and biogeographical affinities with the remaining species of Palpostilpnus than with Townostilpnus chagrinator Aubert, 1961 ( Aubert 1961, 1980; Di Giovanni & Scaramozzino 2019), we hereby transfer it back to Palpostilpnus .

The characteristic body shape is another diagnostic feature of Palpostilpnus , with the head being short and depressed, and the mesosoma stout and obliquely sloped. The PCA derived from geometric morphometric data ( Fig. 4B ) clearly shows that the shape of the mesosoma in species of this genus is fairly distinct from all other analyzed species. The results also support the division of the species recognized as Palpostilpnus into two reasonably clear species groups. Both show the distinctive features of the genus such as the long palp, the needle-like ovipositor and the obliquely sloped mesosoma. However, one group shows a somewhat elongated (more than 1.4 times as long as its height) and strongly slanted mesosoma (e.g., P. ranui sp. nov.), while in the other group the mesosoma is very short, stout (1.25–1.4 times as long as its height) and only slightly obliquely slanted (e.g., P. singaporensis sp. nov.). While it is unclear whether these two groups represent reciprocally monophyletic units, we suggest that they are informally designated as two species groups: (1) the palpator group for the “stout” species, including P. angkor sp. nov., P. brevis , P. maculatus , P. palpator ( Aubert, 1961) , P. papuator , P. rufinator stat. rev., P. singaporensis sp. nov. and P. striator ; (2) the hainanensis group for the “elongated” species, including P. aki sp. nov., P. angka sp. nov., P. hainanensis sp. nov., P. mangrovi sp. nov., P. pterodactylus sp. nov., P. ranui sp. nov., P. rotundatus , P. tamasek sp. nov. and P. trifolium sp. nov.

We have also encountered specimens that show a similar habitus to the species of Palpostilpnus recognized herein, with a depressed head and a short, stout, obliquely sloped mesosoma. However, these species lack the long palpi observed in the species of this genus. Hence, we prefer to wait for a comprehensive phylogenetic assessment of the species of Palpostilpnus and similar taxa before deciding upon the placement of these species.

Biology

Unknown.

Distribution

Oriental and Australasian. Known species are recorded from Brunei, China (Hainan, Hong Kong, Jiangxi, Yunnan), Indonesia (Sulawesi), Malaysia ( Sarawak), Philippines, Singapore and Thailand in the Oriental region and Papua New Guinea in the Australasian region.

Figures

Fig. 4. Morphometrics. A. Landmarks used for the geometric morphometric analyses, following Santos et al. 2019. B. Two principal components (PC1 and PC2) of the shape space for the mesosoma, plotted over a Procrustes-aligned tangent space. Gray dots represent the general ichneumonid morphospace as represented by 347 species from eleven subfamilies. Orange dots and polygon delimit the morphospace occupied by species of the palpator group, and blue dots and polygon represent species of the hainanensis group. Objects at each extremity of the X-axis are deformation grids representing the mean shapes at the extreme of the first principal component.