Crouching Ranger, Hidden Dragons...

, 31 May 2012

Author Ryan Greaves

Immature broad-bodied chaser basking / Calum Lyle
 broad-bodied chaser / Calumn Lyle

For about a year and a half, Sussex Wildlife Trust's Youth Rangers have been managing an area beside the Foredown Tower, in Portslade. There are a number of community allotments on the site, but our responsibility is to monitor and care for the woodland and the pond. Besides having to do a massive litter clearance, we’ve been battling to control scrub and to prevent vegetation from covering the pond.

Recently, we returned to the site to see how things were going. Despite some dull weather and a rather menacing forecast, we aimed to carry out a pond survey. This basically involves us dipping with nets and then recording what we catch. We began to dip, catching a variety of things, such as beetles, water boatmen, pond skaters and an abundance of newts. We were also catching mayfly, damselfly and dragonfly nymphs. In particular we caught a large number of broad-bodied chaser dragonfly nymphs. They are quite easy to identify as their squat bodies and shaggy exteriors make them appear more like mossy spiders than dragonflies.

The youth rangers carrying out our pond survey at the Foredown allotments. That’s Matt sporting the waders! / Ruth Garner
youth rangers pond survey / Ruth-Garner

We’d been surveying the pond for around 30 minutes when someone noticed the empty skin of one of these chaser nymphs stuck to a grass stem. Once a dragonfly nymph is fully grown (which can take up to five years!), and conditions are right, it begins its metamorphosis by crawling out of the water and up the stem of a plant. The nymph then breaks out of and sheds its outer skin, known as the ‘exuvia’. It begins pumping water into its legs and wings, which stretches them to their adult size. Once full size, the dragonfly begins to forcibly ejecting water and pumping air into the appendages, causing them to harden.

damselfly metamorphosis at Foredown / Elisabeth Darwent
damselfly metamorphosis / Elisabeth-Darwent

After spotting this first exuvia, we noticed another on a neighbouring stem, and next to that one from a damselfly, and then near to that an adult broad-bodied chaser dragonfly sitting on a stem, just above its exuvia. As we looked up from that one clump of grass, we began to see these chaser dragonflies in almost every patch of vegetation around the pond. There must have been well over 50 of them, and they all seemed to be emerging on this same day! It was like witnessing the birth of an alien race.

A freshly emerged, rather pale looking, broad bodied chaser / Ryan Greaves
A freshly emerged, rather pale looking, broad bodied chaser / Ryan Greaves

They were at different stages of their emergence. Some were just breaking from their skin; others were still very pale and hunched up, whilst quite a few appeared almost ready to take off there and then. In the final stages of development, with an excess of oxygen available, colour pigments are produced in the outer skin (or cuticle). This turns the very pale emerging dragonfly into a brightly coloured immature adult. Many species will undergo a secondary colour transformation that informs others they are ready to set up territory, find a mate, and reproduce. The adult dragonfly will only spend a couple of months on the wing.

So it was great to see things really springing to life, especially after we’d been working hard to improve the pond and the surrounding area. We now look forward to seeing what other surprises might pop up as we return to the site over the coming months.

As part of the Sussex Wildlife Trust’s Youth Rangers, we’re a group that enjoys getting stuck in and then letting the wildlife reap the benefit. We meet up every Thursday to carry out practical conservation tasks on a variety of different sites across Sussex, but we’re most often based in Stanmer Park, Brighton.

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