Sequential rearing method from larva to adult water beetles (Coleoptera) using devices created with a three-dimensional printer

Abstract Water beetles are holometabolous, which have a pupal period in their ontogeny. When rearing water beetles in a laboratory, both aquatic and land environments should be provided. We designed and created a new system for rearing water beetles, and tested it with five species. Seven parts of three-dimensional printed objects were assembled to make two containers for a larva and a pupa. The assembled container was half submerged in an aquarium filled with water. When the larva had grown enough for pupation, it spontaneously crossed a bridge to reach land and made a pupal chamber in the soil. The newly emerged adult then left the soil and went back to the container with water. The growth process from larva to adult can be achieved sequentially without human assistance. Most larvae could succeed in landing on the soil and returning to water using this system.