Life history of Laccophilus dikinohaseus Kamite, Hikida, and Satô, 2005 (Coleoptera: Dytiscidae) and its preferences for oviposition substrates

Abstract

We describe the life history of Laccophilus dikinohaseus Kamite, Hikida, and Satô, 2005 using laboratory rearing-based methods to contribute to future ex situ and in situ conservation. At 26 °C, each developmental stage had the following duration: egg, 6–7 days; first-instar, 3–5 days; second-instar, 3–5 days; third-instar in water, 7–18 days; landing to leaving the pupal chamber, 9–11 days; and total duration of the immature stages, 30–44 days. The total larval period was significantly longer than those of L. yoshitomii Watanabe and Kamite, 2018, L. kobensis Sharp, 1873, and L. hebusuensis Watanabe and Kamite, 2020. The maximum complete lifespan (egg to adult death) and adult lifespan (exiting the pupal chamber to adult death) were 792 and 762 days, respectively, indicating that L. dikinohaseus can live for more than two years after the adults exit the pupal chamber. Laccophilus dikinohaseus laid eggs not only in aquatic plants but also in driftwood and withered plants, suggesting a diverse oviposition substrate availability. This is the first study on the immature stages of L. dikinohaseus and lifespan of Laccophilus. We propose in situ conservation measures for L. dikinohaseus based on its findings.