Tuesday, 14 June 2011

Stargate 130611 - The Quest for Broad-bodied Chaser

Opportunity knocked sooner than I had imagined as Indiana Steve called on Sunday evening to ask if I would be interested in joining him (and his faithful hound Tilly) in a quest for Broad-bodied Chasers on Monday.
You bet! Broad-bodied Chaser is one of those early season dragons I hardly ever catch up with. They occur annually at a few sites in the borough but not on my patch, though my only previous encounter with the species was a frustrating irregular glimpse of a wandering male a couple of years back at Far Pasture, and that was more by chance than planning, so now armed with prior knowledge of the mission I did a bit of information gathering:
The species favours shallow ponds with an open aspect, and tends to perch for long periods interspersed with bouts of fast, direct flight (this was certainly the case with my previous encounter).
They are a medium sized dragonfly, with broad, flattened abdomens. Immatures of both sexes are predominantly yellow, the male abdomen turning pale blue, and the female slowly turning brown so more mature individuals can be mistaken for four-spotted chasers, and both sexes maintain bright yellow edges either side of the abdomen.
Immature males and females can be told apart by the shape of the abdomen, female is almost oval, male is more parallel with a tapered tip. The claspers are another diagnostic pointer, the males sprout from the centre of the tip, the females are wider apart (I liken them to cats ears?), and the guide also says that yellow individuals can be mistaken for large wasps, can’t imagine that though.
So to Monday, I was joined by Steve early afternoon and we made for Stargate (not the one of science-fiction, I kid you not, we actually have a place nearby of that name) a nature reserve formed from a former landfill site, with a few ponds.


Stargate Nature reserve
 We park the chariot by the entrance and a short trek to the first pond, which is shallow and open, a good sign, and even better, a yellowish dragonfly is already patrolling the margins. We watch it whizz around, Steve is sure of its identity as he was here yesterday and photographed the same individual. I eventually got a decent fix on it so was happy in my own mind we had a broad-bodied chaser, now to sex it. It disappeared off towards a patch of gorse where Steve had photographed it yesterday, and sure enough, we walked over and there it was, perched up in excellent view, and what a beautiful creature, the bright yellow colouring of the abdomen, the shape, and distance between the claspers said we had a young female, (and the way it posed for photographs just confirmed it was a beautiful young female) though would you believe it, the way it occasionally hovered over plants with a rapid to and fro motion, it resembled a very large wasp! But as you can see from the resulting photos taken from close range, she was very approachable.
Broad-bodied Chaser from above. Rounded shape of the abdomen and distance between
 claspers (though not apparent here) confirm a female, and the pale braces (antehumeral stripes)
on the thorax distinguish it from four-spotted chaser which has none.

in profile
note the yellow edging to the abdomen, true of both sexes

and another

This shot shows the gorgeous colouring at the base of the wings
of this truly beautiful creature

Damsels were once again in short supply, small numbers of common blue, azure and blue-tailed. These too were mainly found around the gorse and consisted predominantly of immature specimens, pale pink/lilac where they will eventually become blue, their black markings the only constant with their mature form. In the main they were a bit camera shy, staying in shelter of the long grass where it was difficult to get a focus on them, but I did manage to snap a female common blue, which shows clearly the bomb-shaped black markings along the top of the abdomen, compared to the straighter edged azure.

Common Blue damsel female, this pink individual is typical of the
colouring in all species and sexes of immature damsels we encountered.
Mature individuals are predominently green or blue, and some immatures
can be yellow (as if there's not enough to think about!) 

We did check out the other ponds, but these are deep, steep-sided pools, not good habitat for broad-bodied chaser, in fact completely devoid of dragon or damsel, but all in all a very good session.
Mission accomplished, Broad-bodied Chaser Libellula depressa (though I’ll still try to get a male)

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