Aspect: As typically seen: long elongated body with sparrow tail. Blue head (as name implies), followed by thick black vertical bar aft the gills and across the perctoral fins, large white v-shaped section followed by one vertical black bar and yellow body down to greenish sparrow-like tail (though yellow body can readily be green) Population: Common Notable feature: Above description refers to terminal male phase. Juvenile phase: yellow body with thick horizontal black line running from snout, across eyes, to tail. Comparatively large black stain on dorsal fin. Intermediate: gradually loses transverse black line and dorsal fin black spot, while acquiring white belly. Environment: Swims around rocks and coral boulders, but are carnivorous. Behaviour: In constant movement.
