Aquatic insect diversity in Japan is declining due to water pollution, invasive species, and habitat loss and modification. As a consequence, many Japanese aquatic insect species have been placed on the Japanese Red List. Helophorus auriculatus Sharp, 1884 (Coleoptera: Helophoridae), one of the ‘Endangered species’ on the Japanese Red List, is a small water beetle that inhabits shallow wetlands, such as small pools in riverbeds and paddy fields. Although it is important to elucidate the life history of endangered species to assist in the recovery of their populations, such ecological knowledge has been scarce for H. auriculatus. Therefore, to clarify the basic life history of this species, especially its phenology and reproductive ecology, we conducted field surveys in paddy field water systems and a rearing experiment in the laboratory. Our results showed that adult H. auriculatus mainly inhabit paddy fields and ditches during the fallow season, and reproduce from autumn to spring. The period from the egg stage to adult emergence required about four months to be completed in the laboratory. Survival from larval hatching to adult emergence was significantly higher at 15 °C than at 20 °C, and only 4.4% of larvae could develop into adults at 20 °C, while 22.7% could do so at 15 °C. We concluded that it is important to flood paddy fields from autumn to spring during the fallow season for the conservation of H. auriculatus.

中文翻译：

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濒临灭绝的日本水生甲虫 Helophorus auriculatus（鞘翅目：Helophoridae）的生活史及其保护意义

由于水污染、入侵物种以及栖息地的丧失和改变，日本的水生昆虫多样性正在下降。因此，许多日本水生昆虫物种已被列入日本红色名录。Helophorus auriculatus Sharp，1884（鞘翅目：Helophoridae）是日本红色名录上的“濒危物种”之一，是一种小型水甲虫，栖息于浅湿地，如河床和稻田中的小水池。尽管阐明濒危物种的生活史以帮助其种群恢复很重要，但对于 H. auriculatus 而言，此类生态知识很少。因此，为弄清该物种的基本生活史，特别是物候和生殖生态，我们在稻田水系中进行了实地调查，并在实验室进行了饲养试验。我们的结果表明，成虫在休耕季节主要栖息在稻田和沟渠中，从秋季到春季进行繁殖。从卵期到成虫出现的时间在实验室中大约需要四个月的时间。从幼虫孵化到成虫出现的存活率在 15 °C 时明显高于 20 °C，只有 4.4% 的幼虫可以在 20 °C 下发育成成虫，而在 15 °C 下可以发育成成虫的比例为 22.7%。我们得出的结论是，在休耕季节从秋季到春季对稻田进行洪水泛滥对于保护黑耳螟是很重要的。从幼虫孵化到成虫出现的存活率在 15 °C 时明显高于 20 °C，只有 4.4% 的幼虫可以在 20 °C 下发育成成虫，而在 15 °C 下可以发育成成虫的比例为 22.7%。我们得出的结论是，在休耕季节从秋季到春季对稻田进行洪水泛滥对于保护黑耳螟是很重要的。从幼虫孵化到成虫出现的存活率在 15 °C 时明显高于 20 °C，只有 4.4% 的幼虫可以在 20 °C 下发育成成虫，而在 15 °C 下可以发育成成虫的比例为 22.7%。我们得出的结论是，在休耕季节从秋季到春季对稻田进行洪水泛滥对于保护黑耳螟是很重要的。