Blood-red dragonfly (Sympetrum sanguineum) is very common in Slovenia and, at the Cerknica Lake, in favorable years, thousands of individuals can be present at once during the summer. Adults are typically 34 to 39 mm long, and their wingspan is about 5.5 cm. Adult males have a reddish face, with long hairs densely covering a brownish-red thorax and a red abdomen. Its abdomen is distinctly tapered in the first third of its length and, in shape, resembles a very slender cone. With the exception of black stripes along the sides of the abdomen and a handful of small black spots at its end, the abdomen of a sexually mature male is completely red. For this species, the legs are entirely black. The bodies of immature males are lighter, orange.
The body of the female is dirty yellow, and her eyes are dark brown. In the middle of the dorsal side of her abdomen runs a thin black line, which on every segment is flanked by a pair of black spots, and on the last two segments of the abdomen this line widens into a stripe in the shape of a drop. The pattern of black stripes also adorns the sides of the abdomen.
The habitat of the blood-red dragonfly is mostly still bodies of water with dense reed vegetation. It is less common in flowing waters.
Adults are most common from June to August, after which their numbers decrease in September.
