BBC Wildlife Magazine
Pondwatch: dragons and damsels
1 CAN YOU TELL THEIR LARVAE APART?
The aquatic larvae, or nymphs, of dragonflies and damselflies look similar at first glance. However, the former are larger. Look closely at their tail. Damselfly nymphs end in three flat, leaf-shaped structures – these are gills that absorb oxygen dissolved in the water and release carbon dioxide. Dragonfly nymphs end in five short spines. Their gills are internal – they obtain oxygen by pumping water in and out of their abdomen.
2 HOW LONG DO THEY LIVE?
Big species, such as the emperor, golden-ringed and hawker dragonflies, usually spend two years as nymphs. In smaller dragonflies and damselflies, the larval stage normally lasts a year. But development time varies according to the local climate, latitude, altitude and pond size. As the nymphs grow, they have to moult their tough skin, shedding the tight old cuticle (body covering) for a flexible new one. They do this up to 15 times. By contrast, adult dragonflies and damselflies live only a few days or weeks.
3 WHAT DO THEY FEED ON?
Dragonfly and damsel nymphs are frighteningly effective pond predators. They all have large, powerful, toothed jaws, attached to the end of a bizarre hinged face mask. This is actually the lower lip, or labium, and it’s articulated like an elbow. When in range, it shoots forwards to snatch prey. Though nymphs may crawl through water weed, or swim about in the water of your ponddipping tray, they are mostly sit-and-wait hunters. Large ones will devour tadpoles and small fish… and each other.