The bright yellow two-striped juvenile fades into a drab brown adult with a yellow tail.
Juveniles are bright yellow with two black stripes running the whole length of the body, one along the back and one from the snout through the eye to the tail, and at about 3 to 5 cm they are among the more conspicuous small fish over a coral slope. Adults reach about 13 cm and lose almost all of it, ending dull brown to grey, darker over the rear body, with a yellowish tail and a dark bar at the tail base. The two stages are logged as separate species often enough to be worth stating plainly.
The species to separate it from is the black damsel Neoglyphidodon melas, whose adult is uniformly blue-black right through the tail with no yellow anywhere and whose juvenile is yellow with a single stripe through the eye rather than two long body stripes. Where both occur they use similar ground, and the tail is the quickest adult check.
It takes zooplankton in the water just off the reef and grazes algae on the substrate, and it is a fish of coral-rich slopes with some water movement rather than of open sediment. Juveniles shelter in branching coral and among rubble and stay within a metre or two of cover; adults range further and are territorial in the manner of the genus without being especially aggressive towards divers. It is regular through the region but noticeably thinner where branching coral is limited, which on the muck coasts means it is confined to the coral patches rather than spread along the slope. Recorded from about 2 to 25 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.