This common and widespread European species is related to the well-known stag beetle. Both sexes resemble the female stag beetle but are smaller [body length of 18 to 32 mm] and uniform blackish. Males have distinctly knobbed antennae, and although their jaws are somewhat larger than those of the females, they are nowhere near as large as those of many other male stag beetles.
Lesser stag beetles are nocturnal and are attracted to lights at night. In the daytime they can be found sheltering amongst rotten wood and leaf litter. The adult beetles have a short life with only one purpose: reproduction. They do not feed but survive on water and plant juices. They are frequently found flying in gardens at dusk. They mate and lay their eggs in a suitable piece of decaying wood.