I've had limited experience of identifying Dragonfly larvae and some, particularly the Hawkers ( Aeshna ), can be tricky. Not just for me but for the more competent Dragonflier. A guy called Steve joined me, he was there primarily to removed troublesome plants, and we chatted. I described the differences and nuances of the Banded Demoiselles i was watching and he gave me interesting info regarding what was in the River Blyth. He was telling me how much the problem with the American Red Signal Crayfish had increased telling me how they would just about devour everything they could eat and that if he put a net in he would expect 4/5 easily. He just happened to have one in his car and in a flash he had returned with said net and plastic bucket. The net was briefly swept through the water 3 times and the contents shown to me. Sure enough there were 6 in the bucket ranging in size but also in there was a Damselfly larvae. I was pretty sure it was a Demoiselle and having checked, it was.
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| Demoiselle nymph. |
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Steve never handled the Crayfish, you need a licence, due to the problems with this species. The only river in Northumberland that is not infected is the River Wansbeck. The Crayfish has been known to move across fields in wet weather conditions to contaminate nearby streams ! A couple of images showing the range in size of the Signals caught. The Banded Demoiselle larvae is between 30 and 40 mm long to give you some idea.
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| The two larger samples were about 50mm long. Note the smaller third one. |
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| Two more tiddlers alongside the Damsel nymph. We saw examples in the river around 100mm long. |
Very interesting that John. I've never seen a demoiselle nymph either but it clearly has the same gangly legs as the adult.
ReplyDeleteIncredible to think there are that many crayfish in the waters, I only once spotted a crayfish on the derwent, I thought it was a lobster it was so big, will have to dig out the photos I took. Didn't know you needed a license to handle the yanks though, thought the authorities would be pleased if you 'took a few out'.
Cheers
Alan M
Apparently because they can spread so easily they don't want Tom, Dick or even Harry handling them and then getting into unaffected waterways. It was interesting when he emptied the net into the bucket but my eyes were immediately drawn to the nymph. I hoped it might be a Damoiselle and was overjoyed when it turned out it was. Had to chuckle at the Male adults. There was about 7 of them chasing each other about on and off (as they do ) and a female was happily ovipositing or "sunbathing" about 10 metres further along the river bank on the other side of the bridge in peace.
ReplyDeleteJohn
Fascinating stuff John, will have to chat about it tomorrow. Got to rest my weary bones now
ReplyDeleteAye,
ReplyDeleteDem bones, dem bones, dem weary bones.