The prodni modrač (Orthetrum cancellatum) is a slender, yet sturdy, swift dragonfly that usually reaches 44 to 55 mm in length, and its wingspan measures about 7.5 cm. Adults, sexually mature males, have a yellowish face, black-green eyes, brown thorax and blue abdomen. The edge along the entire abdomen is adorned with a thin yellow band, the last three segments are black. The tail appendages are also black. Later, when maturity tips into old age, blue males almost completely darken, only the tip of the abdomen always remains black. Young males are colored the same as females, their body is yellow, and the abdomen is adorned with longitudinal black bands. Unlike females, immature males have bright, pale greenish eyes with a brownish tint.
Adult female is yellow, her slender abdomen is adorned with longitudinal black bands. We will not confuse her with a young male, because the female has dark, bluish-brown eyes. An older female darkens and loses the black pattern on the abdomen. Her abdomen becomes greenish-brown and often gains a bluish tint.
The prodni modrač prefers standing or slow-flowing waters with little or no aquatic and shoreline vegetation; it is most common in ponds and gravel pits.
The first adult individuals can appear on warm sites and in warm years even before May, and the main flight period of this species is summer, from June to August.
Males are relentless fighters who, when defending their territory, are not deterred even by a much larger female or mate. Most often we will see them perched on a bare lakeshore or flying at high speed just above the water surface.
