Isoplastus Horn

Isoplastus Horn, 1880: 295; Brown 1937b: 173; Daffner 1988: 301. Type species: Isoplastus fossor Horn, 1880, by monotypy.

Diagnosis. Body strongly convex. Antenna with 10 antennomeres, with strong 3-antennomere club. Mandibles forming semicircle when closed together; left mandible with large tooth in basal one-third. Ventral side of head with distinct antennal grooves below eyes. Mesosternum vertical between the mesocoxae, without median carina. Tibiae strong, widened and shovel-like; protibiae with distinct tarsal grooves, their outer margins with strong spines; outer margins of meso- and metatibiae strongly spinose. Tarsal formula 5-5- 4 in both sexes. Males are distinguished by large tooth-like expansion of lower margin of metafemur.

Distribution. The distribution of the genus is eastern Holarctic; it also occurs in Mexico, with undescribed species in the northern Neotropics (Newton 1998).