Blue damselfly (Platycnemis pennipes) is the only representative of the damselfly family living in Slovenia. The adult is typically 35 to 37 mm long, and its wingspan measures about 4.5 cm.
The male blue damselfly is a light blue dragonfly; the ventral side of its abdomen is also light blue. The dorsal side of its abdomen and thorax is patterned with a black pattern. A notably broad head is adorned by a pair of dark blue eyes. Bright legs are also characteristic. Dirty-white tibiae with a thin longitudinal stripe down the middle (these are often distinctly flattened in male representatives of the genus) are on the sides covered with long delicate spines, giving them the appearance of a feather.
Females have a white body with a pattern of black stripes on the back, but care must be taken when determining sex, as young males are also initially white and only later become blue.
The blue damselfly prefers to inhabit slowly flowing karst rivers with richly vegetated riverbanks, but it is not fussy in choosing its habitat. Therefore it is found practically in all bodies of water, only avoiding forest streams and water bodies above 800 m above sea level.
The majority of adult individuals are in flight in June and July; the first may appear as early as the beginning of May, and the last are flying until September.
