Phosphuga atrata Linnaeus, 1758
POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
SILPHINAE Latreille, 1806
SILPHINI Latreille, 1807
Phosphuga Leach, 1817
This widely distributed Palaearctic species occurs throughout the U.K. north to Orkney and is our most common silphid. Adults live and breed for several years and may be found in a range of generally moist habitats; typically deciduous woodland borders but also parkland, gardens, damp grassland, peat bogs and coastal dunes. Through the winter they may be found under bark, logs and debris or among litter or tussocks etc, often in groups and generally active. They are nocturnal and may be seen on pathways and logs etc. from the first warm days of spring, later they often turn up in the sweep net and occasionally on umbel flowers. During the summer, as the temperature increases, they are rarely seen in the open; they rest under logs etc. with the head held under the thorax, and when disturbed secrete a foul smelling yellow liquid. Both adults and larvae feed upon pulmonate snails and earthworms. The adult beetle will climb onto the shell and bite the snail behind its head so causing it to withdraw and secrete defensive mucus. The beetle then applies a salivary secretion which dissolves both the mucus and the snail tissue, after a short while it then enters the shell and begins feeding. Adults do not fly and are assumed to disperse by walking or with the transportation of timber etc.
10-15mm. The beetles vary in colour from entirely black to almost completely red, and distinctly bronze specimens sometimes occur; when groups of adults are found there is usually a range of colour forms present. An unmistakable species; the combination of produced head and mandibles, which is an adaptation to snail predation, rounded pronotum and longitudinal elytral carinae will identify the species among the U.K. silphids. Antennae 11-segmented; the basal segment longer than the next 3, and 9-11 form an indistinct club. Entire upper surface strongly and densely punctured, those on the elytra stronger and longitudinally confluent. Lateral pronotal margins strongly bordered. Elytral margins explanate from prominent shoulders almost to the apex, the surface with 4 strongly raised carinae; the outer 3 evanescent before the apex. Legs long and stout (although the beetle does not run quickly), tibiae with rows of short spines and setae; each with strong spurs on the inner apical angle. Tarsi 5-5-5, with robust, simple claws.
Silpha atrata brown form