BLACK FLIES (DIPTERA, SIMULIIDAE) IN THE LOWER BASIN OF THE RIVER MORAVA

Black fly communities and black fly fauna in general were the object of a study researching 26 sites spread over the lower basin of the river Morava, with particular reference to the place where it is passing the Borska nizina lowland. 15 black fly species were found to reside there. Regarding distribution and constant occurrence of the recorded species on Borska nizina lowland, three groups could be distinguished. The first group consisted of Simulium ornatum and Simulium erythrocephalum. Their occurrence was constant and extremely high (0.73-0.65). In the second group there were five species of constant occurrence 0.19-0.27. The last group consisted of eight species representing the accessoric part of the black fly fauna of Borska nizina lowland. Ranking of species using the correlation coefficient showed, that four species, namely S. erythrocephalum, S. equinum, S. balcanicum and S. ornatum bore more than 78% of the total information. The other species played significantly less important role. The actual community structure was thus an object of continual change in the proportional representation of S. erythrocephalum and of the pair S. equinum + S. ornatum. This could be explained as due to the complex ecological gradient in the Borska nizina lowland flows.