Entomological Science最新文献

Sexual coercion such as prolonged copulation and harassment by males can impose large costs on females. In tiger beetles (Coleoptera: Cicindelidae), the male grasps the female's metathorax with their mandibles during mating, making it difficult to escape from sexual coercion by males. Here, we observed novel sexual coercion avoidance behaviors in the terrestrial tiger beetle Sophiodela japonica. Females employed two distinct behaviors: escape by entering water during copulation, and resistance on land by assuming a motionless state in a characteristic posture during mounting. The use of water to avoid sexual coercion has not been reported among terrestrial insects, suggesting a remarkable counter-adaptation to male grasping with mandibles. These findings highlight behavioral diversity in female resistance and provide new insights into the evolution of such behaviors across insect taxa.

Mangrove forests form vital interfaces between aquatic and terrestrial ecosystems, supporting a wide variety of organisms, both vertebrates and invertebrates. Although insects have long been underrepresented in mangrove research, particularly compared with studies on plant biology and ecosystem functioning, recent findings suggest that their diversity and ecological importance are greater than previously recognized. Nevertheless, their roles in trophic interactions, especially as prey, remain poorly understood. Here, we document six instances of insect predation from a mangrove habitat on Iriomote Island, the Yaeyama Islands, Japan. These include predation by fish, crabs, spiders, dragonflies, wasps and flies on various insect taxa, some of which are associated with mangrove environments. Although fragmentary, these records indicate that insects contribute to mangrove food webs not only as herbivores and detritivores but also as an important prey resource for a broad range of predators. Our observations underscore the need for further research into insect-mediated trophic relationships in mangrove ecosystems.

New knowledge of the Japanese Scathophagidae is presented. Seven species of the genus Scathophaga Meigen, 1803 are reviewed with a newly recorded S. yakutica Ozerov, 2017 from Japan. Scathophaga hadleyi Ozerov, 2013 is revived from a synonym of S. intermedia Walker, 1849. Scatomyza Fallén, 1810 which was resurrected by Ozerov and Krivosheina (2011) is regarded as a synonym of Scathophaga. A new species of Norellisoma kurahashii sp. nov. is described from Hokkaido. Norellisoma lituratum (Meigen, 1826), Cleigastra leucostoma (Zetterstedt, 1846) and Cordilura grunini Ozerov et Krivosheina, 2017 are newly recorded from Japan. Keys to the Japanese species of Scathophaga, Norellisoma, Cleigastra and Cordilura are also provided.

Haliplidae are a family of small water beetles that play crucial roles in wetland ecosystems, including bioturbation and serving as prey within food webs. In Japan, many Haliplidae species are rapidly declining, and the conservation of their habitats has become an urgent priority. Haliplus basinotatus, a crawling water beetle inhabiting vegetation-rich wetlands, is listed on the Japanese Red List, but its biology remains poorly understood. We conducted field surveys in an irrigation pond and rearing experiments to investigate the life cycle of H. basinotatus. Our results revealed a univoltine life cycle: adults lay eggs in late summer, larvae hatch in autumn and grow over 8 months, and new adults appear the following summer. Furthermore, our findings suggest that adults disperse to surrounding ponds during the summer and congregate in breeding-suitable ponds in the autumn. In conclusion, the conservation of H. basinotatus in irrigation ponds requires maintaining aquatic habitats during winter, appropriately managing vegetation to support charophyte growth, and ensuring habitat connectivity within the network.

Hierodula chinensis Werner (Mantodea: Mantidae), an alien praying mantis species in Japan, has been reported at several sites on the three major islands of Honshu, Shikoku, and Kyushu since the 2000s. Because there are multiple records of this alien species from various regions in Japan, we hypothesized that the species has been introduced repeatedly from multiple source regions. To test this hypothesis, we examined genetic variation in a 1,483 bp sequence of the mitochondrial cytochrome c oxidase subunit I gene in 127 H. chinensis individuals from 40 sites in Japan. The inferred molecular phylogeny based on 18 haplotypes revealed two genetically distinct clades within this species, suggesting high genetic variation in its introduced range. One haplotype was detected at most study sites, whereas 10 haplotypes were each found at only a single site and each was the only haplotype detected at that site. These findings suggest that in each area in Japan, the H. chinensis population was likely established by a limited number of founding individuals, and they imply that multiple localized introduction events occurred in the past. Five haplotypes, however, were found in multiple prefectures, and four of these five were detected both in mainland Japan (Honshu) and on Kyushu or Tsushima Island. The occurrence of these haplotypes in geographically separated regions indicates secondary expansion of this species due to human activities or natural migration.

Environmental DNA (eDNA) is a groundbreaking molecular tool that despite its challenges, offers a powerful and comprehensive method for surveying biodiversity. Insects, as key bioindicators of water quality in river ecosystems, make insect eDNA an especially promising tool for biomonitoring and water management. However, significant issues remain. This review explores historical and ongoing eDNA studies, focusing on the genetic diversity of insects, which underpins eDNA analysis. We address two key issues regarding eDNA metabarcoding: selecting suitable DNA barcoding regions for accurate molecular identification and the importance of DNA databases. A review of 82 papers showed that while the mitochondrial DNA (mtDNA) COI region is widely used, it often amplifies nontarget groups. Regarding primer concordance rates among insects, the mtDNA COI region, mixed nucleotide bases are often used to increase the match rate for insects. In contrast, primers targeting the mtDNA 16S rRNA region actually show higher match rates for insects. In addition, we highlight the critical role of regional DNA databases, particularly for species that exhibit genetic differentiation across regions. Also, using a local database, we demonstrated improved detection sensitivity, underscoring the importance of local databases for accurate species identification. To guide future database construction, we reviewed phylogeographic studies and using the Japanese Archipelago, which is a region with high species diversity, proposed genetic ecoregions that demonstrate genetic regionality globally. Our findings emphasize that insect eDNA is at the forefront of species identification technology, offering immense potential for future applications. With innovative approaches, it could revolutionize biomonitoring tools for diverse ecosystems.

The Japanese species of the genus Synacra Förster are taxonomically revised. In total six species are recognized. Synacra foveata sp. n. is described as new to science based on specimens from Kyushû. The association of the male and female of the new species was confirmed based on the mitochondrial gene cytochrome c oxidase submit I (COI). Three species are newly recorded for Japan: S. atracta Macek, 1995, S. brachialis (Nees, 1834), S. compressigastra Chemyreva & Kolyada, 2020. A new host record for S. paupera is provided for Japan. A taxonomic key to 13 species of Synacra occurring in the Palaearctic region is presented.

The acorns of fagaceous species contain considerable amounts of nutrients, especially within the cotyledons. Seed predation that damages cotyledons, primarily caused by Curculio weevils, has been considered to be an important factor affecting acorn production. We investigated acorn falling patterns and predispersal insect damage in Castanopsis cuspidata (Fagaceae), whose cotyledons began to develop late in the growing season and acorns were covered by a cupule until maturity, from an initial stage of acorn development in two well-developed evergreen forests in Japan: Higashiyama in Kyoto Prefecture and Aya in Miyazaki Prefecture. Based on the identification using appearance and genetic analyses of insects damaging acorns, undescribed Heliozela sp. were dominant, followed by undescribed Eurytoma sp. in immature-sized acorns in both Higashiyama and Aya, whereas Curculio weevils were predominant in mature-sized acorns. Seasonal sampling of acorns from the crowns indicated that larvae of Heliozela sp. and Eurytoma sp. feed on the pericarp of the acorn during early stages of acorn development and that these insects have a multivoltine life cycle. In both Higashiyama and Aya, the total number of acorns damaged by Heliozela sp. and Eurytoma sp. amounted to approximately half of the total number of acorns produced in 1 year, when initial acorn production was considerably less. Our results suggest that a variety of seed-feeding insects can evolve to adjust to acorn growth patterns, and that such insects, in turn, have a large impact on acorn production, even prior to cotyledon development.

The genus Osmia is a promising model for studying sexual selection due to its elaborate mating behavior. However, detailed investigations of mating behavior in Japanese Osmia species remain limited. This study describes the mating behavior of the Japanese mason bee Osmia taurus and examines female receptivity under different conditions to provide foundational data for future research. Mating in O. taurus consisted of three distinct phases: precopulatory (mean ± SD = 277.4 ± 289.3 s), copulatory (17.5 ± 4.4 s) and post-copulatory (3,501.8 ± 1,606.7 s), with a notably prolonged post-copulatory phase. Female receptivity declined with age; over 60% of 0-day-old virgin females mated, whereas no mating occurred in 2–3-day-old virgins. Additionally, females lost receptivity immediately after a single mating and did not regain it even after 7–9 days, strongly suggesting monandry. The results also indicate a rapid decline in female attractiveness after mating, suggesting changes in pheromonal communication. These findings highlight the importance of using newly emerged females in mating experiments and raise intriguing questions about the evolutionary and physiological mechanisms underlying the rapid loss of female receptivity in this species.

Millipedes play a crucial role in forest ecosystems as decomposers of organic litter and as food resources. A few studies have reported that millipedes are preyed upon by fish and gastropods and that assemblages of millipede carcasses can be found in streams. However, the mass entry of millipedes into aquatic environments and the effects of environmental conditions on this phenomenon remain unclear. In this study, we characterized the distribution of millipedes, Parafontaria tonominea (Attems, 1899), in a mountain stream in western Japan and examined riparian environmental conditions at the time of their entry into this stream. From June 7 to November 30, 2022, we surveyed a 650 m stream reach two to three times per week. We discovered a high density of millipede carcasses at a single site (661.3 carcasses/m²). Millipede entry occurred between June 17 and 20. After that period, no millipedes were observed in the stream. Meteorological and hydrological observations in the riparian zone indicated that millipedes entered the stream when there was no rainfall, when the soil was relatively wet, and when the daily minimum soil temperature exceeded 15°C for the first time that year. All individuals observed in this study were juveniles, suggesting that their entry was unlikely to be related to their breeding behavior. Soil moisture and temperature conditions may have been favorable for increased millipede activity. Further research is needed to elucidate the reasons for this mass entry and its ecological significance, based on millipede behavioral traits and soil environmental conditions.