Tuesday, 23 July 2013

Black Darter

A trip up to Dartmoor yesterday to mess around in some ponds collecting some water samples. I found something that I had been looking for for ages - Black Darter (Sympetrum danae) exuvia:

I had a hunch that this was going to be danae but had to wait for it to climb up the stem and leave the exuvia. Actually ended up IDing the dragonfly from the exuvia as it was so young!

When it had hardened off a bit it was clearer that it was a danae.

The key criteria for the exuviae is the short length of the spine on segment 9 (S9) compared to the length of that segment. The ratio on this came out as 0.348 which is consistent with the spine being about a third the length of the segment.

The UK confusion species are S. striolatum (Common Darter) and S. sanguineum (Ruddy Darter). Never found sanguineum exuviae but there were plenty of striolatum for comparison yesterday.

Note the length of the spines compared to danae. The ratio came out at 1.114 on this one which is on the low side but the spine is longer than the segment so should be OK to rule out sanguineum which should be shorter. Also pretty sure that sanguineum does not occur in that area.

This is what the emerger might turn into if it is a male.

1 comment:

  1. Very interesting - I have begun to take more notice of the dragonflies and damselflies I see and to try to ID them. I was very pleased to see and ID my first golden ringed dragonflies recently and today I saw a fantastic emperor dragonfly at Dawlish Warren.