Life history of Laccophilus lewisioides Brancucci, 1983 (Coleoptera: Dytiscidae) and the ecological significance of the larval period of five Laccophilus species

Abstract

Dytiscidae are the largest aquatic group belonging to the order Coleoptera. However, approximately 40% of Dytiscidae members have been threatened with extinction in Japan, and Laccophilus is one of the genera with considerable decline. A description of the life history of these species and their ecological information will contribute to their conservation. In this study, I described the life history of Laccophilus lewisioides Brancucci, 1983 (Coleoptera: Dytiscidae: Laccophilinae) using rearing-based methods under laboratory conditions. I then compared the biology of the larval stages of this species to four Laccophilus species, L. vagelineatus Zimmermann, 1922, L. hebusuensis Watanabe & Kamite, 2020, L. yoshitomii Watanabe & Kamite, 2018, and L. kobensis Sharp, 1873. The developmental period for each immature stage at 26°C was as follows: first instar larva, 4–12 days (n = 16); second instar larva, 5–9 days (n = 15); third instar larva, 5–10 days (n = 15); landing to pupation, 2–3 days (n = 2); pupation to adult emergence, 4 days (n = 1); and landing to escape, 8–9 days (n = 14). The total larval period was significantly longer for L. lewisioides than for the other four Laccophilus species. The duration of larval period could be strongly related to the duration of stable water level in the reproductive habitat. The coloration of the larval stage varied between species groups, suggesting that the larvae adapt to the surrounding environment and show a camouflage effect. This is the first report on the immature stages in the life cycle of L. lewisioides.