Drosophila mulli is restricted to the island of Hawaii and is known from three locations. Drosophila mulli was described by Perreira and Kaneshiro (1990) and named for William P. Mull, the Hawaiian naturalist who first discovered this species. The head of D. mulli is yellow on the front and covered with light, silvery grey fuzz. The face of the male is characteristically white, while that of the female is brown. The top of the thorax is brownish yellow and lacks conspicuous markings or stripes. The legs are predominantly yellow, and the front legs of males bear three distinct rows of long, curled hairs. The wings are two and one-half times longer than wide, with distinct brown markings at the base and the tip. The length of the body is 0.17 to 0.2 in (4.3 to 5.0 mm), and the wings are 0.17 to 0.19 in (4.3 to 4.8 mm) long (Kaneshiro and Kaneshiro 1995).