Photo by Shodo Mtow

Researchers at Meijo University and University of Tsukuba collected and taxonomically re-examined numerous enigmatic jumping bristletails. These were first reported 75 years ago. They observed extreme specialization in the external genitalia of the males and discovered that this species belongs to a unique group, potentially representing a primitive state leading to "copulation" during evolutionary development.

Tsukuba, Japan—Insects account for 75% of all animal species, making them the most diverse animal group. Of these, 99% belong to Pterygota, which have acquired wings, while the remaining 1% consist of primitive groups collectively known as Apterygota. Apterygota, which have not yet evolved wings, include Protura, Collembola, Diplura, Archaeognatha, and Zygentoma. Jumping bristletails are a subgroup of Apterygota that are approximately 15 mm long. They feed on green algae that grow on land and inhabit damp, shaded environments such as moistened rock faces and tree bark. It is hypothesized that the ancestors of terrestrial insects initially fed on algae that advanced onto land simultaneously. Jumping bristletails retained many primitive traits, such as the morphological characteristics, providing significant insights into early insect evolution.

Approximately 75 years ago, Halomachilis kojimai (Japanese name: kojima-ishinomi) was described in Akkeshi, Hokkaido. However, the description was inadequate. Additionally, this genus has been considered not inhabiting Japan, necessitating a re-examination. In this study, researchers collected numerous specimens of jumping bristletails identified as the same species and clarified their taxonomy. The findings revealed that this species belongs to the genus Petrobiellus Silvestri, which is endemic to the Far East and includes only a few known species. A detailed examination confirmed that this species exhibits unique characteristics, contributing to the understanding of innovations in mating behavior essential for the evolutionary transition of insects to terrestrial life.

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This work was supported by the JSPS (Japan Society for the Promotion of Science) KAKENHI: Grant-in-Aid for JSPS Research Fellow, JP20J00039 to SM; Grant-in-Aid for Scientific Research C, 19K06821 to RM.

Original Paper

Title of original paper:

What are Halomachilis akkesiensis and Halomachilis kojimai described from Hokkaido, Japan? (Insecta: Archaeognatha: Machilidae)

Journal:

Zootaxa

DOI:

10.11646/zootaxa.5543.3.10

Correspondence

Visiting Researcher MACHIDA Ryuichiro
Sugadaira Research Station, Mountain Science Center, University of Tsukuba

Assistant Professor MTOW Shodo
Department of Agrobiological Resources, Faculty of Agriculture, Meijo University

Related Link

Sugadaira Research Station, Mountain Science Center, University of Tsukuba