Chevron flanks and a trailing dorsal filament that gives the fish its name.
To about 23 cm, white in front and yellow behind, with two sets of fine dark lines crossing at right angles on the flank, a black bar through the eye, and — on adults — a thread drawn out from the rear of the dorsal fin. Pacific fish, including all those seen here, carry a black eyespot on the dorsal fin; Red Sea fish do not, which is a difference worth knowing when working from a general guide.
Like the vagabond butterflyfish it takes a broad diet of algae, polyps and small invertebrates and tolerates turbid water, so the two are often on the same stretch of reef flat. Pairs are usual. It is unhurried and reasonably approachable, and the filament shows best when photographed slightly from behind and below. Recorded from the shallows to about 35 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.