The new species, named Euceros ibex Hopkins, Nascimento & Santos, is known from six female specimens. Four come from Kibale National Park in Uganda, collected in Malaise traps during a large-scale sampling campaign, and two come from Cameroon, including one freshly collected in 2024 near the village of Ebogo and an older specimen from Nkoemvon held in the Natural History Museum in London since 1980. Until now, the only Afrotropical eucerotine known to science was Euceros madecassus, described from Madagascar in 1934, with a second African species, E. tunetanus, known only from North Africa outside the Afrotropical region.

Eucerotinae is a small subfamily of the wasp family Ichneumonidae, comprising just 51 species in the genus Euceros and a single species in the genus Barronia. Its known distribution has been concentrated mainly outside the tropics, especially in northern temperate regions and temperate Australia. Only one species has been recorded from tropical America, in southeastern Brazil, and tropical Asia was thought to be nearly devoid of records until two species were recently documented from Laos and an apparently undescribed specimen turned up in Thailand.

Part of the reason these wasps have been so rarely recorded may lie in their extraordinary biology, which is unique among ichneumonid wasps and resembles that of the family Trigonalidae. Female eucerotines lay stalked eggs on plants. When a passing caterpillar or sawfly larva brushes against the eggs, the larvae attach themselves to the host. If and when that host is itself parasitised by another ichneumonoid wasp, the eucerotine larva enters the secondary parasitoid’s larva and develops inside it as a hyperparasitoid, a parasite of a parasite.

The Ugandan specimens emerged from an unusually intensive sampling effort. Between 2014 and 2015, one of the authors maintained 34 Malaise traps for a full year in Ugandan forest and farmland, collecting 876 roughly two-week samples of flying insects, equivalent to 382.4 trap-months of sampling. Four Eucerotinae were found and pinned while other subfamilies were being processed, and the authors note that many more specimens likely remain unsorted in the bulk samples, unavailable for study for years to come.

To confirm the African wasp was genuinely new, the team compared it with photographs of the holotype and other specimens of E. madecassus from Madagascar, with morphological characters codings from earlier taxonomic work, and with DNA barcodes from public databases. Objective clustering of COI barcode sequences showed that the Ugandan and Cameroonian specimens differ from each other by 3.67 percent, a level that exceeds thresholds commonly used for preliminary species delimitation in insects. However, morphological differences between the two populations are minor and inconsistent, and the Cameroonian lineage is represented by only two partially damaged specimens, so the authors conservatively treat them as a single species pending further material.

The genetic evidence for species-level distinctiveness from Madagascar is much stronger. The two available specimens of E. madecassus differ from each other by only 0.75 percent in their COI sequences, yet both differ from the new species by more than 10 percent. No other COI sequences in the Barcode of Life Database came closer than 8.28 percent divergence. Morphologically, E. ibex can be distinguished from the Malagasy species by the pattern of lateral black spots on the metasoma: the Ugandan specimens carry spots from the second tergite onwards and the Cameroonian specimens lack them entirely, whereas E. madecassus shows spots from the third tergite onwards. The authors caution, however, that some published information about E. madecassus is contradictory, and they suspect several undescribed species may be hiding under that name.

The description itself is rich in technical detail. The holotype female has a fore wing length of 8.7 millimetres, a convex clypeal margin with no clear clypeal sulcus, a face about 1.3 to 1.4 times as wide as high, and antennae with 33 flagellomeres that are slightly flattened and broadened near the middle. The fore wing lacks vein 3rs-m, has a single bulla on vein 2m-cu, and carries a very short ramulus. The propodeum lacks a pleural carina, and the submetapleural carina is expanded anteriorly into a rounded lobe. The general colour is yellow with black markings on the mandibular teeth, head, mesoscutum and metasomal tergites, though the authors suspect much of the variation among specimens, from bright yellow to dark or burnt ochre, reflects fading or preservation effects rather than true colour differences. The species epithet, chosen by readers of the first author’s local newspaper who voted among five suggested names, refers to the ibex-like shape of the antennae.

The wider significance of the find is biogeographical. Earlier assumptions that Eucerotinae is nearly absent from the tropics were partly built on the belief that the subfamily, and its possible sister group Brachycyrtinae, were missing from the mainland Afrotropics, an idea now known to be incorrect for both. The authors argue it is exceedingly unlikely the subfamily is absent from the Democratic Republic of the Congo, which lies between Uganda and Cameroon. The ancestors of the mainland species presumably spread either from Madagascar to the mainland or in the reverse direction, and a Malagasy origin is considered more likely if the subfamily’s Gondwanan history, as proposed by earlier workers, holds up.

Why has such a widespread group gone unnoticed for so long? The answer, the authors suggest, is simply very low abundance combined with insufficient sampling. A rough estimate from the processed Ugandan material suggests tens of individuals rather than hundreds across the entire year of trapping, whereas some common Ugandan ichneumonid species number over a thousand specimens. Low abundance appears to be the norm for the subfamily across its range, perhaps a consequence of its highly specialised hyperparasitoid life cycle, and small-scale African sampling campaigns have simply been unlikely to catch it. Globally, the picture remains uncertain: the subfamily is still most diverse in northern temperate regions and temperate Australia, and the case for a genuine near-absence in tropical America is stronger, since extensive Malaise trapping, host rearing and canopy fogging in Peruvian and Ecuadorian Amazonia, the tropical Andes and Costa Rica have all failed to record eucerotines. The authors speculate that high tropical predation pressure on larvae exposed on leaves, or competition with the biologically similar and tropically diverse Trigonalidae, might explain the pattern, but they emphasise that far more extensive collecting is needed before any confident estimate of global eucerotine diversity can be made.

Subject of Research: First record of the parasitoid wasp subfamily Eucerotinae from the mainland Afrotropics and description of the new species Euceros ibex

Article Title: First record of the subfamily Eucerotinae ( Hymenoptera , Ichneumonidae ) from the mainland Afrotropics, with a description of a new species

Article References: Hopkins, T., Nascimento, A., Santos, B. F., Hovorka, T., Sääksjärvi, I. E., & Österman, E. M. (2026). First record of the subfamily Eucerotinae (Hymenoptera, Ichneumonidae) from the mainland Afrotropics, with a description of a new species. ZooKeys, 1295, 359–374. https://doi.org/10.3897/zookeys.1295.212026

Image Credits: AI Generated

DOI: 10.3897/zookeys.1295.212026

Keywords: Eucerotinae, Euceros ibex, Ichneumonidae, parasitoid wasps, hyperparasitoid, Afrotropics, Uganda, Cameroon, DNA barcoding, taxonomy, new species, Malaise trapping