Serrognathus alcides

Serrognathus alcides is a broad, flattened black stag beetle from Sumatra, also widely known as Dorcus alcides. Males occur in long- and short-jawed forms; long-jawed adult males have elongated mandibles. Adults feed on tree sap and accept soft fruit in captivity. Females lay eggs in decaying hardwood, and larvae develop in wood-rich substrate.

Captive breeding requires suitable rotten hardwood and separate larval containers. Pairings need supervision because males can injure females. Large body size does not guarantee that a male develops the long-jawed form.