Larvae of the water scavenger beetle, Hydrophilus acuminatus (Coleoptera: Hydrophilidae) are specialist predators of snails

Abstract

Hydrophilus acuminatus larvae are known to feed on aquatic prey. However, there is no quantitative study of their feeding habits. In order to determine the feeding preferences and essential prey of larvae of H. acuminatus, both field and laboratory experiments were carried out. Among the five potential species of prey, Austropeplea ollula (Mollusca: Lymnaeidae), Physa acuta (Mollusca: Physidae), Asellus hilgendorfi (Crustacea: Asellidae), Palaemon paucidens (Crustacea: Palaemonidae) and larvae of Propsilocerus akamusi (Insecta: Chironomidae), the first instar larvae of H. acuminatus strongly prefered the Austropeplea and Physa snails in both cafeteria and single-prey species experiments. Larvae that were provided with only snails also successfully developed into second instar larvae, while larvae fed Palaemon, Propsilocerus larvae or Asellus died during the first instar. In addition, the size of adult H. acuminatus reared from first-instar larvae and fed only snails during their entire development was not different from that of adult H. acuminatus collected in the field. This indicates that even though the larvae of H. acuminatus can feed on several kinds of invertebrates, they strongly prefer snails and without them cannot complete their development.

Keywords

• coleoptera
• hydrophilidae
• hydrophilus acuminatus
• feeding preferences
• snail specialist