2urn:lsid:arphahub.com:pub:45048D35-BB1D-5CE8-9668-537E44BD4C7Eurn:lsid:zoobank.org:pub:91BD42D4-90F1-4B45-9350-EEF175B1727AZooKeysZK1313-29891313-2970Pensoft Publishers10.3897/zookeys.1266.175534175534Research ArticleIchneumonidaeFaunistics & DistributionIdentification keySpeciationSystematicsTaxonomyCenozoicNeogeneAfricaReview of the genus Xanthephialtes Cameron (Hymenoptera, Ichneumonidae), with re-definition of the genus and description of a new species from UgandaÖstermanEmil M.emoste@utu.fihttps://orcid.org/0009-0008-8307-58041ConceptualizationWriting - original draftWriting - review and editingInvestigationProject administrationResourcesVisualizationHopkinsTapanihttps://orcid.org/0000-0002-2256-00981Writing - original draftWriting - review and editingData curationFunding acquisitionResourcesSääksjärviIlari E.https://orcid.org/0000-0002-8107-56071Writing - review and editingFunding acquisitionSupervisionKaunistoKari M.https://orcid.org/0000-0001-6665-00471Writing - review and editingVisualizationvan NoortSimonhttps://orcid.org/0000-0001-6930-974123Writing - original draftWriting - review and editingVisualizationBiodiversity Unit, Zoological Museum, University of Turku, 20014 Turku, FinlandUniversity of TurkuTurkuFinlandResearch and Exhibitions Department, South African Museum, Iziko Museums of South Africa, PO Box 61, Cape Town, 8000, South AfricaSouth African Museum, Iziko Museums of South AfricaCape TownSouth AfricaDepartment of Biological Sciences, University of Cape Town, Private Bag Rondebosch, 7701, South AfricaUniversity of Cape TownCape TownSouth Africa
Corresponding author: Emil M. Österman (emil.m.osterman@gmail.com)
Academic editor: Bernardo Santos
202605012026126641533E0F92F7-E44E-5490-9A36-96421EC0A1F11322021D-0C64-48C6-8364-CE9B6B72F4D42010202516122025Emil M. Österman, Tapani Hopkins, Ilari E. Sääksjärvi, Kari M. Kaunisto, Simon van NoortThis is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.https://zoobank.org/1322021D-0C64-48C6-8364-CE9B6B72F4D4
Xanthephialtes Cameron, 1906 (Hymenoptera, Ichneumonidae, Pimplinae) is a small Afrotropical Darwin wasp genus with only two previously known species, for which we provide images of the holotypes. Here, we describe a new species of the genus, X.iidasp. nov., which is also the first record of the genus in Uganda. We provide a re-definition of the genus and a key to species along with notes on the morphological variation and mimicry of X.schoutedeni Benoit, 1954. Online Lucid identification keys and images of all the species treated herein are available at http://www.waspweb.org.
AfricaDarwin waspKibale National Parkmorphological variationtaxonomyUganda Malaise trapping 2014–2015Suomen Kulttuurirahasto501100003125https://ror.org/027xav248http://doi.org/10.13039/501100003125Oskar Öflunds Stiftelse501100005763https://ror.org/0446gjc92http://doi.org/10.13039/501100005763Alfred Kordelinin Säätiö100008969https://ror.org/0107h6s84http://doi.org/10.13039/100008969Suomen Akatemia501100002341https://ror.org/05k73zm37http://doi.org/10.13039/501100002341Opetus- ja Kulttuuriministeriö501100003126https://ror.org/02w52zt87http://doi.org/10.13039/501100003126the Entomological Society of Finland, Svensk-Österbottniska samfundet, Waldemar von Frenckells stiftelseCitation
Österman EM, Hopkins T, Sääksjärvi IE, Kaunisto KM, van Noort S (2026) Review of the genus Xanthephialtes Cameron (Hymenoptera, Ichneumonidae), with re-definition of the genus and description of a new species from Uganda. ZooKeys 1266: 41–53. https://doi.org/10.3897/zookeys.1266.175534
Introduction
Xanthephialtes Cameron, 1906 is a small genus within the tribe Ephialtini of the Pimplinae subfamily of Darwin wasps (Hymenoptera, Ichneumonidae). Until now, the genus included only two known species: X.oculatus (Brullé, 1846) and X.schoutedeni Benoit, 1954 (Dal Pos et al. 2023; Bánki et al. 2025). Previous records of the genus are from Burundi, Guinea, the Democratic Republic of Congo, and South Africa (Dal Pos et al. 2023), suggesting a widespread distribution across continental Africa. Unfortunately, there are no known host records for species of this genus.
Xanthephialtes can easily be distinguished from other pimpline genera (particularly Dolichomitus Smith, 1877, to which it bears some resemblance) by the combination of the following characteristics: ventral mandibular tooth conspicuously longer than dorsal tooth (Fig. 3); flattened bristles on foretibia short and stout (Fig. 4); mesosoma mostly impunctate, with weak punctures in some areas; first tergite depressed, almost impunctate, and lacking latero-median carinae (modified from Townes 1969). The ovipositor is relatively long and apically downcurved (Figs 1, 5), similar to that of some species of Dolichomitus. However, as Dolichomitus seems to be absent from Africa, there is little risk of confusion with other pimpline genera.
In this article, we describe a new species, Xanthephialtesiida sp. nov., from Uganda, provide a re-definition of the genus and images of the holotypes along with a key to species, and include notes on the morphological variation and mimicry of X.schoutedeni. This article is the first in a series of forthcoming publications describing new pimpline species collected in an extensive one-year sampling in Kibale (reported in Österman et al. 2025a).
Methods
The Ugandan Xanthephialtes specimens studied here were separated from samples collected with 34 Malaise traps that operated for one year (2014–2015) in Kibale National Park, Uganda. The traps were placed in various habitats that varied across a successional gradient from primary forest to farmland. The sampling effort totaled 382.4 trap months, of which 22.6 trap months were damaged samples or otherwise provided at most a partial catch of Pimplinae. The study area and sampling campaign are described in greater detail in Hopkins et al. (2019a, 2019b).
We photographed the Ugandan specimens, including the new holotype, at the Zoological Museum, Turku (ZMUT) using a Sony Alpha 9 Mark II camera body mounted on a macro rail, which enabled us to control and incrementally move the camera between shots. Photos were captured using an extension tube, a relay lens, and Mitutoyo Plan Apo objectives with magnifications ranging from 2.5× to 5×. We captured multiple images at successive focal depths and combined them using the software Helicon Focus v. 7.7.5 (Helicon Soft Ltd.) to produce composite layer images with extended depth of field. We carried out final image adjustments in Adobe Photoshop CC to ensure accurate representation of the specimen’s morphological features. Observation at ZMUT were made using Olympus SZ61 and SZX16 stereomicroscopes. Morphological terminology follows Gauld (1991) with minor modifications: dorsal/ventral instead of upper/lower when referring to the mandibular teeth and ovipositor valves.
Images of the other holotype specimens were captured in 2003 with a Nikon SLE2, 105 mm macro lens, and 35 mm slide film. Images acquired at the South African Museum, Cape Town (SAMC) used a Leica LAS 4.9 imaging system, comprising a Leica® Z16 microscope (using either a 2× or 5× objective) with a Leica DFC450 Camera and 0.63× video objective attached; diffused lighting was achieved using a Leica LED5000 HDI dome; and the imaging process, using an automated Z-stepper, was managed using the Leica Application Suite v. 4.9 software installed on a desktop computer.
Repositories
MNHNMuséum national d’Histoire naturelle, Paris, France
RMCAMusée Royal de l’Afrique Centrale, Tervuren, Belgium
SAMC South African Museum, Iziko Museums of South Africa, Cape Town, South Africa
ZMUTZoological Museum, Biodiversity Unit, University of Turku, Turku, Finland
Ephialtesoculatus Brullé, 1846, by original designation.
Re-definition.
Medium-sized to large insects (forewing length 6.5–19 mm) which are generally black and orange-yellow. Clypeus clearly separated from face, impressed, with a deep median notch on apical margin. Mandible basally strongly tapered, apically rather weakly tapered; mandible base oblique, about 28–34° from vertical axis of face, ventral mandibular tooth conspicuously longer than dorsal tooth. Palpal formula 5:4. Occipital carina complete but rather weak. Mesosoma polished with sparse and weak punctures. Epomia weak or absent. Mesoscutum mostly bare, with notauli weakly impressed. Epicnemial carina reaching the level of the middle of the posterior margin of the pronotum. Scutellum convex, without lateral carinae. Propodeum moderately long and rather evenly declivous in profile, with complete pleural carina and posteriorly with short, stub-like lateral longitudinal carina. Submetapleural carina complete. Flattened bristles on foretibia short and stout, numbering about 5–14. Forewing vein 3rs-m with two bullae, enclosing an obliquely trapezoidal areolet, and cu-a opposite base of Rs&M. Hindwing with abscissa of Cu1 between M and cu-a straight and about long as cu-a. First tergite depressed, almost impunctate, and lacks latero-median carinae. Second tergite large, longer than first tergite, with latero-basal, oblique grooves extending to 0.6 length of tergite or more, and with posterior transverse grooves. Tergites 3–5 with smooth latero-median tubercles. Female with ovipositor cylindric, about 4× as long as hind tibia, apically downcurved; ventral valve does not meaningfully enclose the dorsal valve; apex of ventral valve bearing many strong teeth, with a disproportionately large gap between the basal and the second most basal tooth.
This species can be distinguished from all other species of the genus by the basally uncoloured wings and entirely black metasomal tergites. This species is also distinctly smaller than its only known congeners: X.oculatus and X.schoutedeni.
Description.
Female: forewing length about 6.6 mm. Head polished. Malar space about 0.3× as long as basal mandibular width; mandible base oblique, about 34° from vertical axis of face. Lower face about 1.2× as wide as medially high, bearing very weak setiferous punctures. Flagellum with 21 flagellomeres; F1 about 1.35× as long as F2. Head, in dorsal view, with gena evenly rounded behind eye. Lateral ocellus separated from compound eye by about 1.25× its own maximum diameter; ocelli forming a subequilateral triangle, with distance between anterior and posterior ocellus about 0.7× of distance between posterior ocelli. Mesosoma polished. Pronotum mostly bare, with very weak epomia. Mesoscutum bare except for short, sparse hairs on margins. Mesopleuron mostly bare, with short, sparse hairs ventrally and near dorsal margin. Metapleuron bare except for short, sparse hairs on margin at posterior side. Propodeum in profile rather evenly and strongly declivous, dorsally bare, laterally bearing very weak setiferous punctures. Hindwing with abscissa of Cu1 between M and cu-a about 1.1× as long as cu-a. Metasoma polished. Tergite 1 in profile rather low, evenly declivous on basal 2/3 and rather flat on apical 1/3, smooth on declivous part, otherwise with short, sparse hairs, about 1.4× as long as apically broad. Tergite 2 with weak setiferous punctures on median more or less triangular area, delineated by lateral oblique grooves extending from the anterior margin to about 0.6 length of tergite, and rather weak posterior transverse grooves, setiferous punctures outside median area comparably dense and strong except for on smooth posterior band, about 0.95× as long as apically broad. Tergites 3–5 covered with rather dense and strong setiferous punctures except for on smooth posterior band and on nearly smooth latero-median tubercles. Ovipositor projecting beyond apex of metasoma by about 4.0× length of hindtibia, shaft straight, followed by downcurved apical part; apex of ventral valve bearing about 14 teeth, progressively becoming weaker and more oblique from the apex towards the base, with a disproportionately large gap between the basal and second most basal teeth, approximately twice the distance between the second and third most basal teeth.
Colour: head yellow-orange with black mandibular teeth, ocellar area to central occiput and antenna except for yellow apex of apical flagellomere. Mesosoma yellow-orange with stub-like lateral longitudinal carinae on posterior propodeum black; foreleg yellow; midleg blackish with yellow coxa, femur and dorsal trochanter, and trochantellus; hindleg black with yellow-orange basal margin of coxa, dorsal trochantellus and dorso-basal patch on femur; wings uncoloured with forewing infumate distal of blackish pterostigma, encompassing a weakly yellowish apical patch, and hindwing weakly infumate in apical fourth. Metasoma blackish with white membranous areas of sternites.
Male. Unknown.
Etymology.
This species is named in honour of the first author’s wife, Iida Österman, who has shown interest in her husband’s work on Darwin wasps.
Distribution.
Uganda.
Biological notes.
The host(s) are unknown but could be wood-boring insects judging by the similarity of the ovipositor to Dolichomitus. The specimens were mainly caught in primary or to a lesser extent disturbed forest, with few caught in clearcut former plantations and none outside the forest in farmland. However, the sample sizes are too low to tell if this apparent preference for undisturbed forest is a genuine pattern (manuscript in prep). Considerably more were caught during the dry seasons than the wet seasons (22 versus 7 specimens), which is a very common pattern in the (Malaise-trapped) Ugandan material.
AnimaliaHymenopteraIchneumonidae09C367A7-D86B-5C2A-A8EC-39D1BE37CA9CXanthephialtesoculatus(Brullé, 1846)Figs 6–10, 11–16EphialtesoculatusBrullé, 1846: 81. Original description and combination.Xanthephialtesoculatus; Cameron 1906: 118. New combination (indirect).Holotype.
In Muséum national d’Histoire naturelle, Paris (MNHN).
Type locality.
“Afrique Australe” [South Africa].
Material examined.
Holotype • 1 female. South Africa; presumably collected sometime during 1818–1820; Pierre Antoine Delalande leg.; MNHN. Non-type • 1 female. South Africa; SAM-HYM-P000047; SAMC.
The host(s) and other biological information are unknown. The hosts could be wood-boring insects judging by the similarity of the ovipositor to Dolichomitus.
The host(s) are unknown but could be wood-boring insects judging by the similarity of the ovipositor to Dolichomitus. The Ugandan specimens were mainly caught in primary forest and seemed to be concentrated around two traps (HILLT1 and R93T2), which were next to the canopies of recently fallen trees. Other traps with dead wood nearby (e.g. CCT1) did not catch noticeably large amounts of specimens.
The Ugandan specimens differ significantly in colouration compared to the holotype (see Discussion).
Discussion
Unfortunately, information on host use is not available for any species of Xanthephialtes. We suspect that species of Xanthephialtes may, like many other ephialtines with long ovipositors, be idiobiont ectoparasitoids of wood-boring holometabolan insects. Ecological analyses of the Ugandan samples (in prep.) tentatively suggest that both X.schoutedeni and X.iida are associated with undisturbed forest rather than farmland, and X.schoutedeni were caught in much larger numbers in two traps near recently fallen trees (HILLT1 and R93T2). However, otherwise there was no strong association with dead wood for either X.schoutedeni or X.iida, and the sample sizes are mostly too few for statistically significant results. The shorter ovipositor (on an absolute scale) of X.iida suggests it does not oviposit as deep as its congeners, even though the substrate is probably the same.
All 73 Xanthephialtes wasps examined here are female. This is an extremely skewed sex ratio for at least X.iida and X.schoutedeni (we only examined two X.oculatus). The likeliest explanation is that the males swarm around a few female emergence sites, and no such swarm sites happen to have been sampled. Male swarming is common in parasitoids of wood-boring hosts (cf. Eggleton 1991; Keronen et al. 2021), and other such species in the Ugandan material have shown similar skewed sex ratios (e.g. the rhyssine Epirhyssauelensis with 158 females and 2 males; Hopkins et al. 2019c).
In addition to the 29 specimens of X.iida, the Ugandan samples contained 41 specimens which we have identified as X.schoutedeni. The Ugandan specimens differ in colouration, particularly in the wings, compared to the holotype from Tshikapa, Democratic Republic of Congo (Figs 17–19 vs Fig. 22). Most notably, the Ugandan specimens have basally black wings, whereas the holotype has basally yellowish wings with weakly developed blackish areas near the centre of fore- and hindwings, indicating weak development of the Ugandan colour pattern (note how the wings being stacked in Fig. 22 makes them appear even darker). Two other differences between the Ugandan specimens and the holotype are evident: the apical yellow patch on the forewing is larger and the metasoma is more brownish (vs reddish) in the Ugandan specimens. The previously known distribution of X.schoutedeni (the Democratic Republic of Congo, and Guinea) suggests it is widespread in Africa and, therefore, is expected to occur in Uganda. Although, with the deterioration of the connection between Kibale and the forest of the Congo Basin (Hartter 2007), rapid allopatric speciation may be ongoing (see more below). For now, in the absence of DNA samples, we interpret these differences as exceptionally strong intraspecific variation.
The darker colouration of the Ugandan specimens of X.schoutedeni may be explained, for example, by its involvement in a local mimicry ring that favours darker forms. Namely, in the Ugandan samples its colouration (roughly: head and forelegs yellow, mesosoma and remaining legs black, forewing black with a medial and preapical yellow patch, hindwing black with a preapical yellow patch, metasoma reddish) is matched in Pimplinae by a few species of Camptotypus Kriechbaumer, 1889 and Xanthophenax Saussure, 1892 and in Braconidae: Braconinae by at least one species of Mesobracon Szépligeti, 1902 (Fig. 23) and one species from another unidentified genus. Mimicry rings in tropical parasitoid wasps can be taxonomically broad, complex and involve overlapping Batesian and Müllerian mimicry (Porter 1978; Quicke 2015). One possibility is that these ichneumonids are Batesian mimics of Braconinae species with strong chemical defenses, which in turn may mimic each other through Müllerian mimicry; alternatively, all these may mimic aculeate wasps. Establishing the structure of mimicry rings in insects is difficult, however, so this remains speculative.
https://binary.pensoft.net/fig/1505723Key to species of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Xanthephialtes">Xanthephialtes</tp:taxon-name-part></tp:taxon-name></italic> Cameron, 1906
1
Wings basally uncoloured (A); metasomal tergites entirely black (B)
Xanthephialtesiida sp. nov.
–
Wings basally yellowish (a) or blackish (b); metasomal tergites not entirely black (c)
2
2
Mesosoma entirely orange (A); metasomal tergites orange with black tergites 5+ and apico-lateral spots on mid tergites (B); wings basally yellowish (C)
Xanthephialtesoculatus (Brullé, 1846)
–
Mesosoma mostly black (a, b); metasomal tergites brownish (a) or reddish with black apico-lateral spots on mid tergites (b); wings basally yellowish (c) or blackish (d)
Xanthephialtesschoutedeni Benoit, 1954
Acknowledgements
We are grateful to Donald Quicke for identifying the Mesobracon specimen. The collecting in Uganda was supported by Heikki Roininen, Isaiah Mwesige, and the staff of the Makerere University Biological Field Station. Countless people helped process the Ugandan samples, including the staff of the Zoological Museum of the University of Turku, students of the university, and school pupils from the Turku region. These contributions are gratefully acknowledged. The required research and export permits were issued by the Uganda National Council of Science and Technology (NS 504) and the Uganda Wildlife Authority.
Additional informationConflict of interest
The authors have declared that no competing interests exist.
Ethical statement
No ethical statement was reported.
Use of AI
No use of AI was reported.
Funding
The collecting, processing, and publishing of the Ugandan material was supported by the Alfred Kordelin Foundation, the Entomological Society of Finland, the Finnish Cultural Foundation, Oskar Öflunds Stiftelse, Svensk-Österbottniska Samfundet, and Waldemar von Frenckells stiftelse (grants to Tapani Hopkins). The Ministry of Education and Culture (Finland) and the Research Council of Finland funded Emil M. Österman’s doctoral research through the Sustainability Transformations Doctoral Education Pilot when writing this article.
Emil M. Österman https://orcid.org/0009-0008-8307-5804
Tapani Hopkins https://orcid.org/0000-0002-2256-0098
Ilari E. Sääksjärvi https://orcid.org/0000-0002-8107-5607
Kari M. Kaunisto https://orcid.org/0000-0001-6665-0047
Simon van Noort https://orcid.org/0000-0001-6930-9741
Data availability
All images presented in this paper, as well as supplementary images, are available on WaspWeb at https://www.waspweb.org. The data of the Ugandan wasps is in the Zenodo repository (Österman et al. 2025b, https://doi.org/10.5281/zenodo.17379158).
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