New Discovery Led by SNS Post: Parasitic Wasp on Praying Mantis Egg Sac Found for the First Time in Japan! ~A New Form of Discovery Connecting Citizen Observation and Expert Research~

Overview

- In this research, prompted by an observation photo posted on social media, we have recorded the parasitic wasp Eupelmus curvator (family Eupelmidae) in Japan for the first time, a species previously recorded only once in China.

- Taisuke Kawano, an associate researcher at Kyushu University Museum, who specializes in the taxonomy of parasitic wasps, conducted a detailed examination based on social media posts and revealed for the first time in the world that this species parasitizes praying mantis egg sacs. This marks the first record of this species in Japan and sheds light on its ecology.

- This research demonstrates how new discoveries can emerge from the collaboration between citizen observations and experts, and is expected to be an important methodology for future biodiversity research.

Publication Information

Journal: Travaux du Muséum National d’Histoire Naturelle “Grigore Antipa” Title: When your posts yield biodiversity findings: social media-facilitated discovery of Eupelmus (Eupelmus) curvator Yang (Hymenoptera, Eupelmidae) in Japan with notes on its bionomics Authors: Taisuke Kawano, Shunsuke Imada, Shogo Noguchi and Kanji Toyosaki DOI: 10.3897/travaux.69.e171809

Background and History of the Research

Hymenoptera is an order of insects with approximately 150,000 known species worldwide, but many more remain undiscovered, with estimates suggesting the final species count could exceed one million, making it an extremely diverse group. While bees and wasps are well-known, parasitic wasps, which are only a few millimeters in size, are said to account for about 70% of all Hymenoptera. Due to their extremely small size, discovering and recording these parasitic wasps in the wild is difficult, and their distribution and ecology are not well understood. However, parasitic wasps are important not only as natural enemies of pests and as biological pesticides but also as indicators for evaluating biodiversity, making the elucidation of their diversity a significant challenge. Records of wasps parasitizing praying mantis egg sacs, in particular, are limited both domestically and internationally, and were largely unknown in Japan.

In recent years, the spread of social media has led to the widespread sharing of photos and videos of organisms taken by general observers. This has resulted in the accumulation of observational records from locations and times that researchers cannot typically survey.

In the spring of 2021, Shogo Noguchi (then an undergraduate student at the Faculty of Agriculture, Kyushu University) of the Graduate School of Systems Life Science, Kyushu University, posted videos and images on social media (formerly Twitter, now X) of a Eupelmidae wasp laying eggs on a praying mantis egg sac at the Ito Campus of Kyushu University. Associate researcher Taisuke Kawano of the Kyushu University Museum, who specializes in the taxonomy of parasitic wasps, took notice of this post.

As observations of Eupelmidae wasps parasitizing praying mantis egg sacs are extremely rare, Dr. Kawano put out a call for information on social media. As a result, records of similar wasps photographed in parks in Kanagawa Prefecture in 2017 and 2018 by writer Kanji Toyosaki (Nihon Yachubyo no Kai) were received, along with a specimen collected in the spring of 2021 from Nokonoshima island in Fukuoka City by Shunsuke Imada, a curator at the Shiga Prefectural Lake Biwa Museum (then a graduate student at the Graduate School of Agricultural and Environmental Sciences, Kyushu University).

Research Content and Results

Upon detailed examination of the provided specimens and social media photos, it was revealed that these wasps were a species of Eupelmidae, Eupelmus curvator (see reference figure), of which only a few individuals were previously known from Shaanxi Province, China. This marks the first record of this species in Japan, making Japan the second country in the world to confirm its presence. While this species was recorded in China as a parasite of bark beetles (Order Coleoptera), in Japan it has so far been confirmed to parasitize only the egg sacs of the praying mantis species Tenodera aridifolia (Order Mantodea). This suggests that the species may parasitize insects from different orders.

Generally, small wasps that parasitize praying mantis eggs are known to include species from the family Eurytomidae and the genus Anastatus in the family Eupelmidae. On the other hand, the genus Eupelmus is a group that primarily parasitizes the larvae and pupae of other insects, and cases of parasitizing eggs are extremely rare.

The genus Eupelmus is a large group with approximately 1,000 known species, but including this species, only five have been reported to parasitize praying mantis egg sacs, with many of these considered incidental records. However, this species has been confirmed to parasitize praying mantis egg sacs multiple times in different locations, suggesting it likely utilizes praying mantis eggs as its primary host. This indicates that this species has a highly unique ecology even within the genus Eupelmus.

Furthermore, based on the video taken at the Ito Campus of Kyushu University, the detailed oviposition behavior was also elucidated.

Left: Eupelmus curvator, female (from Kawano et al. (2026); scale bar is 1mm) Center: Eupelmus curvator, male (from Kawano et al. (2026); scale bar is 1mm) Right: The Twitter (now X) post that led to the discovery

Future Prospects

In recent years, with the miniaturization and improved performance of camera equipment and the widespread adoption of photography techniques, even amateur photographers can now record small insects, about a few millimeters in size, with astonishingly high detail. Furthermore, with the spread of social media, the sharing of such observational records is rapidly increasing the opportunities for information from non-expert observers to be utilized in biodiversity research. This trend is spreading globally, with reports of new species discoveries and updated distribution records resulting from social media posts. In Japan, species such as Meteorus stellatus (a parasitic wasp) and the mites Ameronothrus twitter and Ameronothrus retweet, named after social media, have been discovered thanks to social media posts, indicating that collaboration between citizen observations and experts is contributing to the creation of new knowledge and becoming a new trend in citizen science.

This research is an example demonstrating that observational information shared via social media can lead to new discoveries, and it is expected that an increase in such "observational eyes" through social media will be a significant method for advancing the understanding of insect diversity that has been overlooked until now.

This discovery was made in urban parks and university campuses. This shows that even in these familiar places, there are still many unknown organisms present right under our feet. What is important is not just the existence of these organisms, but the significant change in "how we find them."

In the future, it will be necessary to clarify the distribution range, host range, and detailed life history of this species. In particular, given that the species was recorded only from beetles in China but has only been confirmed from praying mantis eggs in Japan, verification of its host selection range and regional ecological differences is required. Furthermore, since current domestic records are limited to Fukuoka and Kanagawa Prefectures, distribution surveys in other regions are also an important task.

Comments from Researchers

"A casual post on social media can lead to an unexpected scientific discovery. This research has shown that new knowledge can be gained through the collaboration of citizen observations and experts. I believe that many unknown biodiversities still exist in our immediate environment. Your post might also be the trigger that significantly changes the common understanding of science!" (Taisuke Kawano, Associate Researcher, Kyushu University Museum)

"This species has not yet been discovered in Shiga Prefecture, but I believe it will be found soon. We look forward to receiving reports of your discoveries." (Shunsuke Imada, Curator, Shiga Prefectural Lake Biwa Museum)

Glossary

(※1) Parasitic wasp - Among the Hymenoptera, this is a group that lays eggs on other insects, etc., and whose larvae grow inside or on the surface of the host. The organism being parasitized is called the "host." The larvae feed on the host to grow, often causing the host's death. This way of life is called "predatory parasitism" and plays a role in maintaining population balance in nature, and is also used in agriculture for pest control.

(※2) Biological pesticide - Materials such as natural enemies and microorganisms used in agriculture and forestry to control pests and diseases. Compared to chemical pesticides, they are considered to have a lower environmental impact and higher safety, and are used for sustainable pest management.

(※3) Bark beetle - Insects belonging to the subfamily Scolytinae of the family Curculionidae (Order Coleoptera). They live by boring holes into trees and use wood by breaking it down with the help of symbiotic microorganisms. Large outbreaks can cause damage to forests.

(※4) Order (Moku) - A rank in biological classification, positioned above family (Ka) and below class (Ko). Organisms belonging to the same order share common morphological characteristics and evolutionary origins.

(※5) Host (Kishu) - See explanation for parasitic wasp (※1).

Other

This material is being released simultaneously with the following collaborating institutions and organizations. (Regarding the discovery of this species) Shiga Prefectural Lake Biwa Museum Curator: Shunsuke Imada Tel: 077-568-4811 Fax: 077-568-4850 (Regarding the content of this paper) Graduate School of Systems Life Science, Kyushu University Department of Biological Sciences Professor: Haruki Tatsuta Tel & Fax: 092-802-4275 Mail: [email protected]