Hydrobasileus croceus S hw 43 mm. Unmistakable hw marking easily visible in flying insect. . Lowland lakes, swamp forest margins and larger, well vegetated ponds and drains in open country. Adults sail conspicuously, seldom perching. Translucent larva with very long posterior and dorsal spines on abdomen,  pelagic among sub-surface water weed. Widespread in tropical Asia.

Hydrobasileus croceus is a large, heavy species (hw, 40-43 mm) with a distinctive brown mark at the anal angle of the hind wing easily visible in flight. The anal loop is uniquely club-shaped. It is found mainly in the lowlands on well vegetated lakes and marshes including open areas in black water peat swamp. Males soar back and forth patrolling large territories. The female is similarly marked, but less strongly.