The type of Hydrometra abbreviata Fabricius, 1803 is a well-preserved fifth instar larva belonging to Gerris thoracicus as suggested by Stål (1868a). Since Hydrometra abbreviata Fabricius, 1803 is a senior synonym of Gerris thoracicus Schummel, 1832, action should be taken to preserve the latter, well established name. The identity of Gerris abbreviata (Fabricius) sensu Latreille, 1804 is uncertain, but in any case this name is unavailable (J.T. Polhemus, pers. comm.).