Pierwsze dane z monitoringu stanu populacji łątki ozdobnej Coenagrion ornatum (Selys, 1850) w dolinie Sieniochy (Śniatycze, Polska południowo-wschodnia)

Coenagrion ornatum is a critically en- dangered dragonfy species in Poland known nowadays from only one site (three others given after 1990 extinguished). The authors discuss frst data (2007–2008) doming from regular observations of the last known popu- lation discovered in 2007 r. in Śniatycze near Zamość (50°38’–50°39’ N, 23°32’ E, UTM square: FB71). The Ornate Bluet inhabits one of draina- ge ditches in the area of a spring fen of cal- careous character (Fig. 1). Molinietum caeruleae and Caricetum appropinquatae are dominating in vegetation, in some places Cladietum marisci and Schoenetum ferruginei, associated with shallowly situated calcareous substratum, are also preserved. The described fen is systematically burnt-out to- gether with surrounding meadows. The ditch with C. ornatum has no direct connection with springs. Its water is war- mer, slightly impoverished in oxygen and more fertile than spring waters (Tab. 1). During the warmer winter in 2007 ice layer did not cover the whole water surface – it was present only in sides. In the cooler win- ter in 2008 layer reached the thickness of 5 cm and covered the whole water surface, however, the ditch were not frozen to the bottom. The ditch is shallow (a few cm), narrow (the width of water surface up to 1m, ho- wever, in many places only to 20–30 cm), the bottom is covered with muddy substra- ta. Current is slow, water transparent. The bottom is grown by Berula erecta: in varied density from a single plant to compact clusters. In large part of the watercourse the expansion of Phragmites communis and Carex appropinquata is visible, banks are grown by single scrubby willows in some places. In the front part of the ditch water is covered by moss mats. Regular observations were conducted in the year 2007, from the moment of disco- very of the site and through the whole year 2008. The ornate bluet was noted during 11 controls (Tab. 2). Maximum number of in- dividuals was 195, they inhabited the stretch of ditch with length of ca. 170 m – with Berula erecta the least choked by Phragmites communis and Carex appropinquata. The period of imaginal fight lasted from the last decade of May till the last decade of July (individuals observed on 3 June were very numerous and partially mature therefore their emergence must have taken place seve- ral days earlier). It is a relevant supplement to the previous data from Poland. This cor- responds with the data from Czech Republic and is similar to data from other countries of Central and Eastern Europe. The features of habitat correspond with these in literature. The fact that the species is resistant to ice layer seems to be important (however, water must be