1. Fore wing very narrow with apex distinctly pointed; its length at least 14× its width, disk with only a single line of setae. Antenna with placoid sensilla (PLS) on each claval antennomere attached to surface almost their entire length subgenus Hydrophylita.2 1 ʹ Fore wing wider, with apex slightly pointed; its length less than 10× its width, disk densely setose. Antenna with one or more PLS on each claval antennomere spinelike, attached to surface only at the base ........................ ........................ subgenus Lutzimicron.3 2. Antenna with one anellus (North America).. ................................................... H. aquivolans 2 ʹ Antenna with two anelli (Central and South America) ................................ H. bachmanni 3. Antenna with 8 antennomeres, C2 and C3 completely fused. (Asia) .... .... H. emporos 3 ʹ Antenna with 9 antennomeres, C2 and C3 separate ............................................................ 4 4. Antenna with funicular antennomeres approximately equal in length, first claval antennomere (C1) approximately equal in length to first funicular antennomere (F1); clava poorly differentiated from funicle. Fore wing 8× as long as wide (Brazil) ... ....................................................................................................................................................... H. lestesi 4 ʹ Antenna with F2 and C1 both distinctly shorter than F1, clava well differentiated from funicle. Fore wing 6× as long as wide (broadly distributed in Neotropics)... H. neusae

Published as part of Lin, Chun-Yu, Hsu, Yu-Hsun, Wang, Jo-Fan & Lin, Chung-Ping, 2019, New damselfly hosts and species identification of an aquatic parasitoid Hydrophylita emporos (Hymenoptera: Trichogrammatidae) in Taiwan, pp. 2195-2205 in Journal of Natural History 53 (35) on pages 2195-2205, DOI: 10.1080/00222933.2019.1694714, http://zenodo.org/record/3654869