Heinrichiellus belongs to the subfamily Ichneumoninae and is distinguished by a combination of morphological traits, including the absence of an antennal cavity, extremely long and thin maxillary palps, a sharp sternaulus on the mesopleuron, very long and slender legs, and a long, rounded rather than flattened metasomal petiole. Its higher classification has been uncertain because several of these traits are unusual for the tribe Platylabini, to which the genus had previously been assigned.

The Indian material came from Yingku in Arunachal Pradesh and the Biligiri Rangaswamy Temple Tiger Reserve in Karnataka. Yellow pan traps collected specimens at the former site, while Malaise traps collected material at the latter. The Thai specimens came from Doi Chiang Dao National Park in Chiang Mai and were collected as part of the Thailand Inventory Group for Entomological Research project. Specimens were examined and imaged with digital microscopes and stereomicroscopes.

The new Thai species, H. brevispinus, is represented by a female holotype and a male paratype. The female has a body length of 11.7 mm and a fore wing length of 8.6 mm. Its name refers to its characteristically short propodeal apophysis, or spine-like projection. The species also has an area basalis that is not defined by carinae, a sharply defined sternaulus and an incomplete juxtacoxal carina.

Heinrichiellus natgeo, known from a female holotype and a male paratype in Arunachal Pradesh, has a female body length of 10.7 mm and a fore wing length of 7.7 mm. Diagnostic features include a very large fore wing areolet that hardly narrows anteriorly, a propodeal spiracle 1.4 times as long as wide, long and sharp propodeal apophyses and an elongated area superomedia. The species name honors the National Geographic Society for supporting the Siang Expedition during which the specimens were collected.

The third new species, H. vedani, was described from a female holotype and four paratypes collected in the Biligiri Rangaswamy Temple Tiger Reserve. The female holotype measures 6.0 mm in body length and 4.5 mm in fore wing length. It can be distinguished from H. brevispinus by a yellow ventral half of the clypeus, a malar space 1.9 times as long as the basal width of the mandible, and a first tergite 4.5 times as long as its anterior width. The name honors Vedan, a singer from Kerala whose music is described by the study as inspiring reflection, unity and dialogue.

For the first assessment of the genus using molecular data, the researchers sequenced cytochrome oxidase I, 16S rRNA and 28S rRNA from H. natgeo. They combined these sequences with ultraconserved-element data from an earlier Ichneumoninae analysis, producing a hybrid matrix of 298 terminal taxa and 2,682 base pairs. Maximum-likelihood analyses placed Heinrichiellus firmly within Ichneumoninae but outside Platylabini. Instead, the genus was placed within Ichneumonini, in a polytomy with Plagiotrypes concinnus and Imeria seyrigi.

Support was maximal for the placement of Heinrichiellus within Ichneumonini, whereas support for its exact sister-group relationship was low. The researchers suggested that limited sequence data, represented by only the three newly analyzed loci, may explain the unresolved relationship, rather than a genuine hard polytomy. The analysis also showed that some morphology previously used to place genera in Platylabini, including a convex clypeus and a large hypopygium, can occur in Ichneumonini and has evolved repeatedly.

The study provides a revised generic diagnosis and an identification key for the five recognized Heinrichiellus species: H. brevispinus, H. natgeo, H. vedani, H. hildegardae and H. nambui. Their documented distribution now includes the Eastern Palaearctic in Russia and Japan and the Oriental region in India and Thailand. The hosts of Heinrichiellus remain unknown, and the molecular analysis was limited to a single newly sequenced species and three Sanger loci, restricting resolution of its closest relationships.

Subject of Research: Taxonomic and phylogenetic assessment of the ichneumonid wasp genus Heinrichiellus in India and Thailand

Article Title: First report of the genus Heinrichiellus Tereshkin, 2009 ( Hymenoptera , Ichneumonidae ) from the Oriental region with the description of three new species

Article References: Ranjith, A. P., Broad, G. R., Santos, B. F., & Butcher, B. A. (2025). First report of the genus Heinrichiellus Tereshkin, 2009 (Hymenoptera, Ichneumonidae) from the Oriental region with the description of three new species. Journal of Hymenoptera Research, 98, 757-778. https://doi.org/10.3897/jhr.98.158760

Image Credits: AI Generated

DOI: 10.3897/jhr.98.158760

Keywords: Heinrichiellus, Ichneumonidae, Ichneumoninae, taxonomy, phylogenetics, new species, Oriental region, India, Thailand, molecular analysis, First, report