Half-Olympian son of Zeus by the Arcadian nymph Callisto; eponymous founder of Arcadia and ancestor of the Arcadian kings. Came near to matricide on his mother — by then transformed into a bear — before Zeus translated both into the constellations Ursa Major and Boötes, where they eternally pursue each other across the northern sky. The Lycaon-banquet variant transfers the Tantalus-Pelops motif to Arcadia and supplies the etiology of the werewolf-rite at Mt. Lycaon. The civilizing-hero attributes (agriculture, weaving, bread) mark Arcas as the structural founder-ancestor of the Arcadian people in the standard heroic-age pattern.