A new species of Darwin wasp has been described from Finland, and it was hiding in plain sight inside one of Europe’s most intensively studied insect faunas. The species, named Lochetica ramii, belongs to the Ichneumonidae, the enormous family of parasitoid wasps known as Darwin wasps because their diversity helped inspire Charles Darwin’s reflections on the natural world. The discovery, published in the Deutsche Entomologische Zeitschrift, raises the number of known species in the small genus Lochetica to five and comes with a complete identification key to all of them.
The genus Lochetica is what taxonomists call species-poor: until now, only four species were recognised worldwide, all restricted to the Holarctic region encompassing Europe, northern Asia and North America. For much of the twentieth century, scientists knew of just two species, Lochetica westoni and Lochetica pimplaria, until the latter was synonymised with the former in 1972. A revision in 1983 added two more species, Lochetica farta from Taiwan and Lochetica agonia from the western United States, and in 2021 Lochetica japonica was described from Japan. Apart from L. westoni, every species in the genus is known from only a handful of specimens, and the biology of most of them remains a complete mystery.
The story of the new species began when the author of the study noticed that Finnish museum collections appeared to contain two tentatively distinct morphological forms of Lochetica, even though only a single species, L. westoni, had ever been recorded in Europe. To resolve whether these forms truly represented different species, he assembled a dataset of 88 specimens drawn from museum collections in Helsinki, Lund, Norwich and Odawara, as well as a private collection in Finland. The material included type specimens from the original nineteenth-century descriptions, examined through high-resolution photographs, allowing direct comparison with specimens collected as far back as 1928.
The morphological evidence centred on two quantitative characters. The first, the ovi-tib ratio, compares the length of the ovipositor projecting beyond the tip of the metasoma with the length of the hind tibia. The second, the temple ratio, compares the width of the temples behind the eyes with the maximum width of the head. Statistical comparison using the Welch t-test revealed striking differences. The mean ovi-tib ratio was 2.8 in L. westoni but only 2.1 in the new species, a difference so pronounced that the effect size, measured by Cohen’s d, reached 5.3. Remarkably, no overlapping specimens were found for this character, although the gap between the species is narrow: the maximum recorded for the new species is 2.4 and the minimum for L. westoni is 2.6.
The temple ratio also differed significantly, averaging 0.95 in the new species against 0.88 in L. westoni, although here numerous specimens overlapped. Beyond the measurements, a suite of qualitative characters separates the two wasps. The new species has weak latero-median carinae on the first metasomal tergite that do not reach the level of the spiracles, weaker crenulae along the sternaulus, and black or dark brown tegulae, the small plates at the base of the wings. L. westoni, by contrast, has strong carinae, stronger crenulae, a longer ovipositor and yellow tegulae. Compared with the Japanese L. japonica, the new species shows a uniformly sloping vertex with almost granulate sculpture, predominantly red legs and reddish mandibles, whereas the Japanese species has deeply punctate head surfaces, nearly black legs and predominantly black mandibles.
Molecular evidence sealed the case. Ten specimens were sequenced for the cytochrome oxidase subunit I marker, the standard DNA barcode region, using a single middle leg from each wasp. Combined with three publicly available sequences from Norwegian specimens, the dataset of thirteen sequences produced a distance matrix and a Neighbour-Joining tree. The results were unambiguous: interspecific distances between the two Finnish forms ranged from 7.12 to 8.05 percent, while intraspecific variation within each form was negligible, at most 0.16 percent in the new species and 0.61 percent in L. westoni. This clean barcode gap, visualised in a phylogenetic tree, is exactly the pattern expected when two reproductively isolated species are compared.
The new species was described from a substantial type series, including a holotype collected in June 2021 on the wall of a log barn beside a meadow near Kuopio, and 37 female and one male paratypes spanning Finland from 60 to 64 degrees north. Its known distribution falls mainly within the boreal forest biome, with a few specimens from the northern edge of the temperate broadleaf and mixed forest zone. The specimens were collected from open biotopes and from coniferous forests, with traps mounted on dead and dying Norway spruce, on burned pine forests, and even on the wall of a log building. Intriguingly, both species occur in the same habitats and sometimes the same locations, but the new species appears more common in shaded, spruce-dominated forests, while L. westoni seems to favour more exposed sites. The author cautions, however, that more data are needed for reliable comparisons.
The study also produced new host records that illuminate the strange life history of these wasps. L. westoni is a parasitoid of Passaloecus, a genus of small crabronid wasps that nest in beetle burrows in dead wood, in galls and in plant stems. The new rearing records published in the study include males and females reared from Passaloecus monilicornis, P. eremita and P. borealis, and the new species itself has been reared from P. monilicornis. Earlier work suggested that the female L. westoni must oviposit while the host nest is still under construction, because her ovipositor is not long enough to pierce the outer resin plug that seals the completed nest. The wasp overwinters as a larva inside a silky cocoon within the host’s nest chamber.
One of the most curious patterns in the genus concerns its males. In the studied material, females outnumbered males dramatically, 38 to 1 in the new species and 40 to 5 in L. westoni. Yet the original reared type series of L. westoni from 1880 contained 15 males against 9 females, suggesting a normal sex ratio. The most likely explanation is that the males are simply short-lived and therefore almost never encountered by collectors, although the difficulty of identifying male Phygadeuontinae may also mean they languish unsorted in museum drawers. Three of the five known species remain known only from females, and the males of two species have never been seen.
The discovery carries a broader message about biodiversity in well-studied regions. If a new species of parasitoid wasp could slip through decades of Finnish collecting, hidden inside a genus with only four known species, then many more await recognition. The author notes that the new species is almost certainly present in neighbouring countries and may have been confused with L. westoni elsewhere, and that future work should examine large amounts of museum material across wide geographic areas. For now, the five known species of Lochetica can finally be told apart, thanks to a combination of careful morphology, vintage museum specimens and a few millimetres of wasp DNA. The species name honours the author’s grandfather Raimo, known as Rami, whose influence kindled a love of nature that ultimately led to the wasp’s discovery.
Subject of Research: Taxonomic description of a new Darwin wasp species, Lochetica ramii, from Finland using morphology and DNA barcoding
Article Title:  Lochetica ramii sp. nov. – a new species of Lochetica Kriechbaumer, 1892 ( Hymenoptera , Ichneumonidae , Phygadeuontinae ) from Finland, with a key to world species
Article References: Paappanen, J. (2024). Lochetica ramii sp. nov. – a new species of Lochetica Kriechbaumer, 1892 (Hymenoptera, Ichneumonidae, Phygadeuontinae) from Finland, with a key to world species. Deutsche Entomologische Zeitschrift, 71(1), 193-208. https://doi.org/10.3897/dez.71.121217
Image Credits: AI Generated
Keywords: Lochetica ramii, Ichneumonidae, Darwin wasps, new species, Finland, DNA barcoding, COI, parasitoid wasps, Passaloecus, taxonomy, boreal forest, Hymenoptera
News Source: Drew Townsend. (October 19, 2026). Hidden in Finnish forests: new Darwin wasp species revealed by DNA barcodes. Scienmag.
