These Stag Beetles, Sinodendron rugosum, sometimes appear on wood piles, as in these photos, though they prefer to remain under the bark of wet, rotting logs. This species, the only one in the genus Sinodendron, occurs from British Columbia Canada through the western states of the US to California.

The Stag Beetles are so called because the mandibles of the male, which may be as long as the body and are branched in some species, bear a fancied resemblance to the antlers of a stag. Sinodendron rugosum, on the other hand, looks somewhat like the Rhinoceros Beetle, a kind of scarab.

All Stag Beetles, Family Lucanidae, are highly sexually dimorphic. Males show the enlarged modifications on the head, while females don’t. However, sex is not always easy to determine without dissection of the genitals because there are males that mimick females, taking the opportunity to mate while their male rivals are fighting over the female. More on the drawing in slide 12.

For a discussion of the general phenomenon of female-appearing males, see Sneaker Males in the Animal Communication Project.