The adults and larvae of some groups in the coleopteran family Carabidae are known to prey on snails (Mollusca: Gastropoda). Most species of the carabid tribe Licinini are believed to feed on live snails. However, the snail-eating behavior of only a few species has been studied. Whether adults of the licinine genusBadistercan prey on live snails was tested by providing 155 live snails of 20 species (eleven terrestrial and nine aquatic species) to adults ofBadister pictusBates, 1873, and observing their behavior under laboratory conditions. Six of the 20 snail species have an operculum that can close the aperture of the shell. EachB. pictusadult attacked all of the snails provided.Badister pictussuccessfully preyed on ten terrestrial and six aquatic snail species. These beetles used their strikingly asymmetrical mandibles to break the dextral shells along the dorsal part of the whorls from the outer lip of the aperture towards the apex, allowing subsequent consumption of the soft bodies. However, 41.9% of snails could not be eaten byB. pictusadults. The rate of predation success byB. pictusdecreased with increasing shell size and thickness of snails. In addition, the presence of an operculum decreased the rate of predation success byB. pictus. The results show that the shell size, thickness, and operculum of some snail species could play important roles in preventingB. pictusmandibles from breaking the shells. Therefore,Badisterbeetles may exert selective pressure on the evolution of defensive shell structures in small-sized snails.
