Bluecheek Butterflyfish

The blue-cheeked butterflyfish, Chaetodon semilarvatus, is a species of butterflyfish (family Chaetodontidae). It is found in the Red Sea and the Gulf of Aden, at depths of between 3 and 20 m.

Its length is up to 23 cm (9.1 in). It is mostly yellow, with thin slate blue vertical lines on the sides and a slate blue cheek patch in lieu of the usual black eyestripe of most Chaetodon.

The blue-cheeked butterflyfish belongs to the large subgenus Rabdophorus which might warrant recognition as a distinct genus. In this group, it seems closest to a group containing the Blackback butterflyfish (C. melannotus), the spot-naped butterflyfish (C. oxycephalus), or the peculiar black-wedged butterflyfish (C. falcula) and Pacific double-saddle butterflyfish or "false falcula", (C. ulietensis). Though the present species does not share their white body with black on the back and caudal peduncle and even lacks the typical eyestripe of Chaetodon, it has the same tell-tale blue vertical lines as these species.