RHYSODIDAE Laporte, 1840
Wrinkled Bark Beetles
ADEPHAGA Schellenberg, 1806
Approx. 20 (worldwide)
Approx. 350 (worldwide)
A small family of about 330 species contained within 20 or so genera. The classification of the family is still being worked out; it has been variously incorporated into the Carabidae on similarities of adult adaptive features e.g. tactile setae, antennal cleaner and structures of the pygidial defence system, but a range of larval characteristics suggest a sufficient justification to place the group in its own family within the Adephaga. They occur in forested regions on all the continents with the largest diversity occurring in northern South America, New Guinea, Indonesia and the Philippines. Both adults and larvae live in damp decaying wood infested with slime moulds upon which they feed. The adults do not burrow but simply push their way through soft layers of wood while the larvae generally live in short tunnels. The adult mandibles lack any cutting edges and are believed to be non functional, instead the beetles move the head from side to side using the mentum to slice off pieces of food. Adult Rhysodids are small, 5-9mm and elongate and most are drab, the colour varying from brown to black. The head is produced forward and narrowed in front of convex and prominent eyes and the vertex is deeply grooved either side of a longitudinal median lobe, the temples are strongly constricted to a narrow neck and this morphology gives them a very characteristic appearance. The antennae are 11-segmented, relatively short and moniliform or weakly filiform. Pronotum with deep longitudinal furrows which are generally open to the basal margin. Elytra with deep, strongly punctured striae to apex. Legs short and, especially the forelegs, robust. Tarsi 5-segmented. The elongate larvae lack terminal urogomphi.
The genus Rhysodes Dalman, 1823 includes 2 species.
Rhysodes comes (Lewis, 1888) From southern Russia and Japan.
Rhysodes sulcatus (Fabricius, 1787) is a rare species and protected in Europe. It has been recorded from the following countries: France, Germany, Hungary, Italy, Poland, Romania, Sweden, Turkey, Ukraine and Russia. It occurs in ancient undisturbed humid forests and, as both the adults and larvae feed exclusively on slime moulds, requires large quantities of decaying wood. Fossil evidence shows the species to have occurred in Britain up to 5000 years ago i.e. before humans began to alter the environment. So far as the UK fauna is concerned the adults are quite distinctive and cannot be mistaken for any other species.