An uncommon species, Hydrellia tarsata Haliday, is recorded from Russia for the first time. Larval habitat, host plant (Stratiotes aloides L.) and braconid parasitoids of this species are indicated for the first time. H. tarsata is shown to develop abundantly within the lake littoral zone. The braconid Chaenusa opaca Stelfox is recorded from Russia for the first time. Hydrellia tarsata (Ephydridae) : Host New record Chaenusa opaca (Braconidae) : Parasite New record Opius caesus (Braconidae) : Parasite Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Habitat; Terrestrial habitat; Land zones; Palaearctic region; Eurasia Chaenusa opaca; Dipteran hosts; Hydrellia tarsata; Riparian habitat; Russia; New record & new dipteran host record; Pskov Province, Sebezh District, Lake Anisimovo Hydrellia tarsata; Hymenopteran parasites; Chaenusa opaca & Opius caesus; Plant hosts; Stratiotes aloides; Riparian habitat; Russia; New record & biology including new plant host & hymenopteran parasite records; Pskov Province, Sebezh District, Lake Anisimovo Opius caesus; Dipteran hosts; New host record; Hydrellia tarsata; Riparian habitat; Russia; Pskov Province, Sebezh District, Lake Anisimovo none