First record of Diamesa thomasi Serra-Tosio, 1970, from Croatia

Abstract

Plitvice National Park is situated in the mountainous karst area of Croatia. When conducting studies of the chironomid fauna of the park, we found that Diamesa thomasi Serra-Tosio, 1970 were abundant in the stream Bjela rijeka. The streams Bijela rijeka and Crna rijeka form the Matica River, which is the main surface-water supplier of the lakes in the park. This is the first record of D. thomasi in Croatia. The river’s source, the Bijela rijeka spring, is located at an altitude of 719 m a.s.l. at 44°50’05” N and 15°33’43” E. The Bijela rijeka spring is a rheocrene that dries out only during extremely dry years (Marusic & Curuvija 1991). Spring water emerges from substrate composed mainly of cobbles and sand with a few interspersed moss-covered boulders. Because of these characteristics, it is considered a psammorheocrene type of spring (Gerecke et al. 1998). The tree canopy is open during spring, and there is much aquatic vegetation and accumulated allochthonous organic material during autumn and winter.