Distinctive Characters: Dorsal fin with 9 spines and 10-11 rays. Anal fin with 3 spines and 10 rays. Pectoral fin with 13 rays. Body depth 4.1-4.7 in standard length. Small scales on cheek, opercle and nape. Lips thick, the lower strongly bi-lobed. Caudal fin truncate to slightly rounded.
Colour: Adults light blue, shading to pale yellowish or white anteriorly, with a black stripe from snout through eye to rear edge of caudal fin. This stripe is progressively broader posteriorly. Juveniles largely black with a narrow bright blue stripe on back which continues onto dorsal part of head.
Habitat and Biology: Commonly seen on upper reef slopes to depths of 40 m. Feeds on crustacean ectoparasites (and mucus) of other fishes.
Remarks: Unlike L. bicolor (previous page), Labroides dimidiatus even enters the mouths and gill chambers of some of the larger host fishes in its cleaning operations. Also establishes “cleaning stations�? on the reef to which host fishes come for its services.