Descriptions of the larvae of Acanthagrion speculum and A. trilobatum from Costa Rica (Odonata: Coenagrionidae).

Description of the final instar of Acanthagrion trilobatum Leonard, 1977 and A. speculum Garrison, 1985 is based on associated specimens from San José, Turrialba and Sarapiquí Provinces, Costa Rica. Illustrations of these two species and a comparative table summarizing the main features of all larvae of Acanthagrion described to date are provided. The larva of A. trilobatum is distinguished from that of A. speculum by shorter lateral caudal lamellae (length 7 mm vs. 8.2 mm), lateral carina of abdominal segments 2-8 with spiniform setae on posterior 1/3 (lateral carinae of only S6-8 with spiniform setae in A. speculum), and male gonapophyses incurved (straight in A. speculum).