Monday, 10 March 2014

Steam Diversity Survey: Invertebrate ID's

Following on from doing the stream diversity in Brecon. We pickled the specimens we caught and then a week or two later we started trying to identify them.

I started with a stonefly (Plecoptera) larvae and a mayfly (Ephemeroptera) nymph.
Its easy to distinguish what is a mayfly or stonefly without using any keys however I did so the first time, just to check and its all good practice I guess. A stonefly will always have two tails whereas a mayfly will usually have three (although some have two). then the gills are the second easy detector to see which it is.

(Right: Stonefly specimen under the microscope)


I used a simple key to find out which family it was. which was the PERLIDAE family. The steps I took are as follows:

  1. 3 tarsals not roughly equal lengths. 
  2. The 3rd tarsal is obviously longer than the first two combined
  3. it has obvious gills at the base of each leg ('hairy armpits')
I then got a stonefly book that goes further tan the family and tried to find the species. It was quite easy as there was only two species in this family and so I narrowed it down to:  Perla bipuncta. (left: My field notebook; rough diagrams of stonefly.)


The mayfly (photos below; under the microscope) was harder to identify than the stonefly. I narrowed it down to the family: HEPTAGENUDAE. It has a pronotum with flange-like extension and its eyes are dorsal. 

Im pretty sure that the species is Ecdyonurus insignis (eaton), however the book for the mayfly ID's wasnt as easy to understand and was harder to distinguish between species. However if you look closely at the underside of the body there are dark marking on the underside of the body (you can see this faintly in the picture to the right).

If you want to see more of these photos go to my flickr: Stream Diversity and Invertebrate ID's

(above: my field note book with 
notes and diagrams of the specimen)

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