"Was it you?" Identity of the culprit who cutting leaves from Fragrant styrax of Seoul National University of Education

In the heart of Gangnam, the Megachile pseudomonticola Hedicke, following the Megachile sculpturalis Smith and the Leucospis japonica, was captured.

Last year, traces were found at Seoul National University of Education where leaves of ginkgo trees were neatly cut in round shapes.

Professor Shin Dong-hoon from the Department of Science Education at Seoul National University of Education, who witnessed this, pointed out that the 'Megachilidae' was the prime suspect through the straight-cut cross section. However, as the culprit's identity has not been definitively revealed as their actual presence was never found.

Then, on the 18th of last month, Professor Shin Dong-hoon captured the fact that the culprit who had been cutting off the leaves of Fragrant styrax was the 'Megachile pseudomonticola Hedicke' and shared a video on the 'Biology Observation—WhyTV' YouTube channel.

Then, what kind of insect is a Megachile pseudomonticola Hedicke?

Previously, the Megachile pseudomonticola Hedicke was known to inhabit only Japan and China. However, it has been revealed by Dr. Lee Heung-sik from the Animal and Plant Quarantine Agency that it also inhabits domestically in South Korea. Afterwards, based on his research paper, it was added to the National Biological Species List.

Dr. Lee Heung-sik stated, "Compared to the past, sightings of Megachile pseudomonticola Hedicke are continuing nationwide thanks to the advancement of the internet and camera equipment. However, compared to other Megachilidae, they are not found often."

The Megachile pseudomonticola Hedicke is often mistaken for the Megachile sculpturalis Smith due to similar appearance and size, but upon closer examination, differences can be observed in various aspects.

Dr. Lee Heung-sik explained, "Megachile sculpturalis Smith has a round and large head, with the front part of its large mandibles being slender. On the other hand, the Megachile pseudomonticola Hedicke has a thin head, but it has well-developed broad cutting surfaces on its mandibles to cut leaves."

In the paper titled <1 Unrecorded species of Korean Megachilidae, Report on Megachile pseudomonticola (Hymenoptera Linnaeus, Megachilidae)> published in the Journal of Korean Beekeeping Society, it is also explained that the large mandible of the Megachile pseudomonticola Hedicke is round and has a cutting surface between the second and third teeth.

Dr. Lee said, "The wing colors also differ slightly. While the wings of the Megachile sculpturalis Smith appear mostly dark brown, the wings of the Megachile pseudomonticola Hedicke have only about the quarter in dark brown at the tips."

He went on to explain, "When looking closely at the abdomen, the Megachile sculpturalis Smith has large and numerous stipples, whereas the Megachile pseudomonticola Hedicke has no stippling on its abdomen.”

Professor Shin conveyed, "The Megachile sculpturalis Smith has one white line on its abdomen, but the Megachile pseudomonticola Hedicke can be observed a white line on each segment."

The two species also differ noticeably in their reproductive methods. In the case of the Megachile sculpturalis Smith, instead of cutting leaves, it places a mixture ball of nectar and pollen into tree holes. Subsequently, it lays eggs on the pollen ball and constructs walls with pine resin. This process is repeated to create multiple egg-laying rooms.

On the other hand, the Megachile pseudomonticola Hedicke, like other Megachilidae, is known to create egg-laying rooms by cutting leaves and placing them into tree holes or crevices in rocks. It lays eggs by collecting pollen inside the rolled-up leaves.

At this time, it is known that the Megachile sculpturalis Smith primarily uses 'kudzu vine' leaves. However, the Megachile pseudomonticola Hedicke observed at Seoul National University of Education is cutting down the leaves of the 'Fragrant styrax'. What happened?

Dr. Lee Heung-sik explained, “They are known to make egg-laying chambers using kudzu vine leaves, but they they are not averse to using any broad leaves as well” and added, "They prefer soft and large leaves because they cut leaves largely."

In fact, the leaves of the Lilytree planted right next to the Fragrant styrax were a little tougher, so no traces of cutting by the Megachile pseudomonticola Hedicke were found, but the leaves of the Fragrant styrax were cut here and there.

Also, because the leaves of the Styrax japonicus, which belongs to the same family as the Fragrant styrax, have small leaves, it was not possible to find traces of the Megachile pseudomonticola Hedicke.

Professor Shin Dong-hoon said, "While it took about 10 seconds for the Megachile pseudomonticola Hedicke to cut a leaf, but it took more time to select a leaf. The Megachile pseudomonticola Hedicke seems to be contemplating in its own way."

He predicted, "Just 2 to 3 weeks ago, it was possible to observe Megachile pseudomonticola Hedicke cutting down leaves, but it's hard to find them recently. It seems like they have finished manufacturing the egg-laying chambers."

He continued, "I was tracking the Megachile pseudomonticola Hedicke as they cut leaves with my eyes, but in an instant, it flew behind a building, and I was unable to determine the location of their oviposition chambers. Finding this is the imminent task ahead."

Meanwhile, at Seoul National University of Education, not only the Megachile sculpturalis Smith and the Megachile pseudomonticola Hedicke, but also the ecology of rare Leucospis japonica is being observed.

A Leucospis japonica is a parasitic bee that finds the egg-laying chamber of a Megachile sculpturalis Smith and then uses its long ovipositor to lay eggs on the larva of the Megachile sculpturalis Smith within.

Professor Shin Dong-hoon, together with his students, is observing and recording the ecology of wild bees such as the Megachile sculpturalis Smith, Megachile pseudomonticola Hedicke, and Leucospis japonica, where they reproduce through competition and oviposition right in the middle of the city. 

Professor Shin mentioned, "Urban ecological observations are effective in enhancing students' ecological literacy, and this ecological literacy can ultimately bolster the capacity to respond to the climate crisis.”