Chironomidae (Diptera) of the Šventoji and Žeimena sub-basins in Lithuania.

Background: Chironomidae, commonly known as non-biting midges, are key indicators of the health and biodiversity of freshwater ecosystems. They are also one of the most abundant and diverse groups of aquatic invertebrates. Although Chironomidae are ecologically important, abundant and diverse, there has been limited focused research on this group in Lithuania. Our study addresses this gap by analysing the diversity of Chironomidae in six Lithuanian streams.

New Information: In this study, we present a comprehensive list of Chironomidae collected from six streams with similar hydrological characteristics: three dammed and three undammed. Lithuania is home to 158 species of known species of Chironomidae, comprised of 22 species in the subfamily Tanypodinae, 87 in the Chironominae, 42 in the Orthocladiinae, four in the Diamesinae and three in the Prodiamesinae. Throughout our research, we collected 11,296 chironomid specimens using a D-shaped aquatic net. Amongst these specimens, we identified 89 species representing 65 genera and five subfamilies, including 37 species and 12 genera, were recorded for the first time in Lithuania. The subfamily Chironominae, with 28 genera and 6,816 specimens, has exhibited the highest abundance of non-biting midges both in terms of genera and individuals. Amongst the streams investigated, the Luknelė was the richest in diversity, harbouring 37 genera and 2,657 individuals, accounting for about 55% of the Chironomidae genera found during the research. Our findings significantly enhance the understanding of the Lithuanian Chironomidae fauna, marking the first comprehensive study of such a kind, as previous knowledge of this fauna has been derived only from related studies.