Ladona exusta (Say) is a small libelluline dragonfly restricted to the Atlantic coastal region of North America from southern Newfoundland to Virginia. Based on 20 nymphs collected in shallow ponds in Massachusetts, New Jersey and New York, we describe the final unknown nymph of the genus. The palps have 5 major setae, differing from its more widespread congeners, L. deplanata and L. julia, which normally have 6 on each side, sometimes 7 (rarely 5 or 8). Nearly all L. exusta nymphs can be separated from L. deplanata using the number of palpal setae (5 v. 6) in conjunction with the ratio of epiproct length to metafemur length (0.42–0.48 v. 0.49–0.67). Ladona exusta is smaller than L. julia in a number of characters, the most distinctive of which are prementum length (3.70–3.90 mm vs. 3.90–4.75 mm) and prementum maximum width (3.35–3.85 mm vs. 3.90–4.85 mm).