Tiny Parasitoid Wasps Reveal Three Hidden Species in South Korea

Deep in the forests of South Korea, some of the country’s smallest predators have been hiding in plain sight. A new study has uncovered three species of parasitoid wasps previously unknown to science, along with two species recorded from the Korean Peninsula for the first time. The wasps belong to the genus Aspilota, a group of braconid wasps so diminutive and taxonomically challenging that even seasoned entomologists regard it as one of the most difficult lineages within the entire subfamily Alysiinae. The discovery, published in the Journal of Hymenoptera Research, brings the number of Aspilota species recognized from Korea to sixteen and offers a rare combined look at both the morphology and the DNA barcodes of these minute insects.

The wasps at the center of the study are anything but ordinary. Measuring between roughly 1.6 and 2.6 millimeters in body length, they are koinobiont endoparasitoids, meaning they live inside their hosts while keeping them alive long enough for the parasite larva to complete its development. Their targets are fly larvae, particularly members of the family Phoridae, the scuttle flies. When the wasp larva is ready to pupate, it must break out of the host puparium, and it does so using a remarkable piece of evolutionary engineering: outward-curved or straight teeth on the mandibles, usually three but ranging from two to seven, that saw through the puparial wall from the inside. This exodont mandible is one of the defining features of the subfamily and a vivid reminder that even the tiniest insects carry specialized tools shaped by millions of years of host manipulation.

The genus Aspilota itself is cosmopolitan, with approximately 250 described species distributed across nearly all zoogeographic regions. Yet its members are notoriously hard to tell apart. Their diminutive body size and the limited number of stable morphological diagnostic characters have long frustrated taxonomists. What reliably distinguishes Aspilota in the strict sense is a combination of two features: an enlarged anterior tentorial depression, a smooth or rugose depression on the head that reaches the inner margin of the eye, and the presence of vein cuqu1, also known as 2-SR, in the fore wing. These characters, subtle as they are, have allowed researchers to separate Aspilota from a genus complex surrounding it that is regarded as one of the most taxonomically difficult groups within the Alysiinae.

Previous records of Aspilota from the Korean Peninsula were based primarily on the works of the Hungarian dipterist and hymenopterist Lajos Papp, who documented eleven species in 2001 and four more in the same year, with a final addition in 2007. A significant proportion of those records originated from North Korea. More recently, three previously recorded species were excluded from the Korean fauna by Sohn in 2026, leaving thirteen species of Aspilota in the strict sense currently recognized from the country. Against this backdrop, the new study by Sohn and van Achterberg examined specimens collected using Malaise traps at sites across South Korea, including Chuncheon-si, Yeoncheon-gun, Pyeongchang-gun, Daejeon and Namwon-si, and sorted and prepared at the Animal Systematics Laboratory of Kunsan National University.

The three new species are Aspilota angusticarinata, Aspilota ocellocarinata and Aspilota laticlypeata, each named for a distinctive anatomical feature. Aspilota angusticarinata, whose name means narrow carina in Latin, was collected on Mount Daeryong in Gangwon-do and is distinguished by the dorsal carinae of the first metasomal tergite being much closer together than in its closest relative, Aspilota austroussurica. Aspilota ocellocarinata, collected at Yeoncheon-gun in Gyeonggi-do, bears deep, rugose carinate depressions encircling the ocelli, the three simple eyes on the top of the head, a feature absent in its relative Aspilota nasica. Aspilota laticlypeata, from Odaesan National Park in Gangwon-do, has a notably wide clypeus, three times wider than high, compared with 1.7 to 1.8 times in its relative Aspilota shiramizui. All three species were described from female holotypes deposited in the National Institute of Biological Resources collection in Incheon.

Beyond the new species, the study recorded Aspilota aniva and Aspilota chanka, both originally described by Belokobylskij in 2007, from South Korea for the first time. The Korean specimens of both species are generally consistent with the original descriptions from the Russian Far East, although minor differences were noted. The Korean female of A. aniva has a 15-segmented antenna compared with 19 segments in the original description, and a mandible 1.3 times longer than wide compared with 1.6 times in the original. The Korean specimen of A. chanka has a fore wing 2.4 times longer than wide, compared with 2.6 to 2.7 times in the original description. These small variations are not unusual in parasitoid wasps and may reflect geographic variation across the East Palaearctic range of these species.

To complement the morphological work, the researchers analyzed the barcode region of mitochondrial cytochrome c oxidase I, or COI, for all five species treated in the study. The team used non-destructive extraction methods, including a slightly modified version of the freezing method, to preserve morphologically complete voucher specimens while still obtaining DNA. The Folmer primer pair, LCO1490 and HCO2198, was used to amplify an approximately 658 base pair fragment from the 5′ region of COI. A total of 586 base pairs were successfully sequenced from each of the five species and deposited in GenBank. Pairwise genetic distances were estimated using the P-distance model with pairwise deletion.

The results of the COI analysis support the morphological distinctions drawn by the researchers. Interspecific distances ranged from 0.076 to 0.096, with an average of 0.083. The lowest distance, 0.076, was observed between A. angusticarinata and A. laticlypeata, between A. angusticarinata and A. chanka, and between A. laticlypeata and A. chanka. The highest distance, 0.096, was found between A. ocellocarinata and A. aniva. These distances, while modest, are consistent with the morphological separation of the five species and provide an independent molecular line of evidence that the new taxa are genuinely distinct rather than variants of a single variable species.

The study also provided an identification key for the Aspilota species recorded from Korea, excluding the subgenus Eusynaldis. The key relies on a suite of morphological characters, including the presence or absence of a medio-posterior depression on the mesoscutum, the relative lengths of the first flagellomere and other antennal segments, the proportions of the hind femur, the structure of the propodeal areola, and the ratios of wing veins such as r, 3-SR and 2-SR. For a genus where species can differ by ratios as small as 1.3 versus 1.5 times longer than wide, such keys are essential tools for future surveys and for researchers attempting to identify specimens without access to DNA sequencing.

The broader significance of the discovery lies in the biology of the wasps themselves. Several alysiine species have been used in the biological control of economically important pest flies, including Liriomyza trifolii, the serpentine leafminer, and Drosophila suzukii, the spotted wing drosophila. While the hosts of the newly described Korean species remain unknown, the confirmed host associations of Aspilota species are primarily with Phoridae, with doubtful records from other dipteran families requiring further verification. As surveys of Korean parasitoid wasps continue, the combination of morphological description, photographic documentation using multi-focusing technology and stacked imaging, and COI barcode analysis offers a template for uncovering further hidden diversity in a group of insects that, despite their small size, play a substantial role in regulating fly populations across the landscapes they inhabit.

Subject of Research: Three new species and two new records of the genus Aspilota Foerster ( Hymenoptera , Braconidae , Alysiinae ) from South Korea

Article Title: Three new species and two new records of the genus Aspilota Foerster ( Hymenoptera , Braconidae , Alysiinae ) from South Korea

Article References: Sohn, J.-H., van Achterberg, C., Kim, S., Kim, Y., & Kim, H. (2026). Three new species and two new records of the genus Aspilota Foerster (Hymenoptera, Braconidae, Alysiinae) from South Korea. Journal of Hymenoptera Research, 99, 857-875. https://doi.org/10.3897/jhr.99.199506

Image Credits: AI Generated

DOI: 10.3897/jhr.99.199506

Keywords: Three, species, records, genus, Aspilota, Foerster, Hymenoptera, Braconidae, Alysiinae, South, Korea, scientific research