Chasers on the Wood Shed

By Andrew Fraser

As I write this (4th July 2000 in Alvechurch) yet another broad bodied chaser Libellula depressa is emerging from its nymphal case attached to the wooden door of our wood shed by the house. This must be the sixth out of about thirty we have seen that has chosen this particular spot for its transformation.

But perhaps some background first. We constructed a small pond about four by two metres including margins in Easter 1999. We planted it up with a wide range of native plants, many "borrowed" from the Worcestershire Wildlife Trust's pond at Lower Smite Farm. With these came some invertebrates and many others have colonised since then. Last summer we saw a female chaser laying eggs in the pool and subsequently found nymphs developing in some numbers, gradually getting larger through the autumn and winter.

On 28th May we found the first adult emerging from the nymph and that on day altogether we found seven. Four more followed the next day and then smaller numbers over about a week. Another, on 10th June, was the first we have seen for several days, but that may have been because it was warm and sunny: the previous few days had been cooler and cloudy.

About seven of the nymphs have chosen plants on the west edge of the pool for emergence, all the remainder have headed off across the lawn and patio towards the house which also lies west of the pool. The furthest walked about 8 metres and climbed 1.5 metres of brickwork before settling down to emerge. They all started leaving the pond early in the morning at about 7 am and could be found walking fairly quickly across the lawn. Being due west, the house is away from the sun at that time in the morning and in most cases they emerged from their nymphs in the shade. Why did they all head in this direction? If they were heading for the darkest area on the horizon, this would actually be to the south where the neighbours have a Leylandii that would appear much darker than our house.

By l0am they were all emerging, which appears to take about an hour. They spent about an hour pumping up their wings and then for the rest of the day hung with their wings back over their bodies, only spreading them out in typical chaser fashion towards the end of the day. Occasionally, on a hot day they would fly late in the day they emerged, but normally it was the following day when they flew if it was sunny, but if it was cloudy or wet they stayed until the next sunny day.

Only one did not manage to open its wings fully and this was eaten by the next door neighbour's cat! Several others disappeared, almost certainly taken by birds, I think blackbirds or starlings. Only pathetic little piles of wings were left as a reminder of their potential beauty.

My friend on the wood shed? Well, 20 seconds ago I saw it pull its abdomen out from nymphal case, so at least it has got that far. When it has hardened off I will move it too a less obvious place so the birds will not be so likely to find it.

P.S. The last chaser we saw emerged on 1st July, much later than the previous last one. Unfortunately, it also fell prey to the cat!