Biology and morphology of immature stages of Coniocleonus nigrosuturatus (Coleoptera: Curculionidae: Lixinae)

Abstract: Mature larvae and pupae of Coniocleonus (Plagiographus) nigrosuturatus (Goeze, 1777) (Curculionidae: Lixinae: Cleonini) are described and compared with three other cleonine taxa with known larvae. The biology of the species was studied in Romania, Hungary and Slovakia. Common Stork's-bill (Erodium cicutarium) (Geraniaceae) is identified as a host plant of both larvae and adults of this weevil. The weevil is very likely monophagous, and previous records of thyme (Thymus sp., Lamiaceae) as the host plant hence appear incorrect. Coniocleonus nigrosuturatus prefers dry, sunny places in grassland habitats, with sparse vegetation, bare ground and patchily growing host plants. Overwintering beetles emerge in early spring (March), feed and mate on the host plants. The highest activity of adults was observed from mid-April to mid-May. Larvae live in the soil in a vertical tunnel near the host plant and feed externally on the base of the stem. Usually, a single larva was observed at an attacked plant, however, sometimes up to 3 larvae were found. At the beginning of July, the larvae pupate in a closed earthen cell. A reared adult emerged in the laboratory at the end of July. We suppose that part of the population overwinters in pupation cells, although some adults leave the cells at the end of summer. They then most likely spend some time feeding on the host plants and look for suitable shelters in which to overwinter later.

Key words: Coleoptera; Curculionidae; Lixinae; Coniocleonus nigrosuturatus; mature larva; pupa; morphology; host plant; Erodium cicutarium; Geraniaceae; larval development; life history; central Europe; Palaearctic Region