Beautiful Demoiselle (Calopteryx virgo) lives in fast flowing rivers across Europe and Asia. It feeds on insects and larvae. Its conservation status is Least Concern.
Fascinating facts about the Beautiful Demoiselle
- Larvae spend up to two years crawling through submerged vegetation, molting through ten to twelve stages before emerging as adults. In their final stage they measure just 3.5-4.6 mm long and weigh about 4 milligrams, barely a speck of dust. Because they cling to plant stems with long-clawed legs, they can survive in fast-flowing streams without being swept away. However, they are extremely sensitive to oxygen drops; only a few days of deprivation cause mortality to spike dramatically. This long, delicate development makes clean, oxygen-rich water essential for their survival.
- A beautiful demoiselle stretches to a body length of 49-54 mm, with hindwings spanning 31-37 mm. Males flaunt metallic blue-green bodies and eyes, while females sport dark brown iridescent wings edged with a white pseudopterostigma. Their large, dark frames and broad wings.
- Male beautiful demoiselles guard tiny river patches from perches on twigs or rocks, repeatedly spreading their wings in a rapid "wing-lapping" display. This flick-flap motion helps to regulate body temperature on sunny days. When a female drifts by, the male darts out, performs acrobatic loops, and then leads her to a suitable plant for egg laying. The male stays nearby, hovering for up to several minutes, to fend off any intruding suitors.
- Because beautiful demoiselles need cool, oxygen-rich streams with specific aquatic plants, they vanish from polluted cities and intensive farms, earning a "stenoecious" label. In Germany's Red Data Book (1998) they are listed as endangered in several states, and similar warnings appear for Austria and Switzerland, even though the IUCN rates the species as Least Concern. Eutrophication from wastewater fuels algal blooms that choke oxygen and smother the plants females need for egg laying. Restoring a narrow strip of vegetation along riverbanks can revive suitable habitat.
- Females can dump a clutch of up to 300 eggs onto floating water-crowfoot, then slip beneath the surface for as long as ninety minutes to hammer each egg into a stem.
Sources
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At a glance
RangeEurope and Asia
HabitatFast flowing rivers
DietInsects and larvae
About the Beautiful Demoiselle
As the sunlight dances across the rippling waters, the Beautiful Demoiselle emerges, its iridescent wings glimmering like polished jewels as it flits effortlessly above the river's edge. With a delicate, almost ethereal quality, this enchanting damselfly navigates the air with a mesmerizing rhythm, its slender body weaving in and out of the lush vegetation that lines the water's edge. As it alights upon a delicate blade of grass, its wings beat at a hypnotic pace, casting a spell of wonder over all who are fortunate enough to behold it.
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