Maechidius arcuatus is a species of beetle of the family Scarabaeidae. It is found in Indonesia (Moluccas), where they occur in disturbed forests and vegetation along streams at altitudes from 50 to 200 meters.
Adults reach a length of about 6-7.5 mm. They have a dark brown, shiny body, with ferruginous legs.
They have been reported feeding on the flowers of Syzigium aromaticum.
The species name is derived from Latin arcuatus (meaning bow shaped) and refers to the shape of the male metatibia.