Hydropsyche larva
using organza gilling technique
by James Matthews

  This time round we’re going to attempt to tie the ever-popular hydropsyche larva, again using my organza gilling technique. As far as I’m led to believe, there are between 12000 – 15000 species of this wee beastie worldwide, give or take a few hundred, with around 200 species in the UK alone. This is probably the most prevalent free-living caddis in our home waters in the UK, and whenever I kick sample or turn over a few stones this is the one I’m most likely to encounter.

  The colouration varies from river to river; the hydropsyches in a chalkstream tend to be a bright, vivid green, not unlike a rhyac, while further north you’ll find a darker, more olive colour.

  Continental hydropsyches can be a milky, creamy beige, through to brown and olive, so again it’s important to check and match the hatch in your local water. What differentiates these from the rhyac is the two anal appendages, and the less heavy segmentation of the body. Also, the gills are on the underside, in two fine rows.

  Anyway, for this pattern you’ll need:

Hook: Partridge K4A, various sizes, or Tiemco 947BL.
Underbody: thin lead sheet.
Thread: any GSP, eg Powersilk, Dyneema.
Body: nymphskin.
Gills and tail appendages: organza.
Legs: golden pheasant centre tail (Veli Autie style).
Colouration: Edding Kurecolour pens or Dylon dyes.

  Tying instructions:

  Clamp the hook in the vice, tie on your thread and go well round the bend.

  Get a few organza strands, and tie in securely, well round the bend. Then with your thread come underneath the trailing strands (this lifts them up). Bring your thread over the top and add a whip finish. Trim the tail ends to a stump.

  Take your nymphskin and cut at a 45 degree angle. Again, tie in securely and leave the thread hanging. Then cut a 1.5 – 2.0 mm wide strip of the lead sheet and wind on your preferred caddis shape (remember to leave plenty of room for the thorax and eye end).

  Tie on another GSP thread and go over the lead windings, then take the thread wraps back to just before the eye, just a couple of millimetres. Now you’re ready to do the body.

  Stretch the nymphskin and pull tightly, then start winding forward, overlapping by 50%, then relax tension slightly, again by 50 % .Overlap until you reach the thorax area and increase tension again. Then tie off with the thread that’s hanging conveniently. Whip finish and snip off the waste.

  Take your first thread, spin it to make a fine rope and follow around the first two segments of the hydropsyche’s body, following into the grooves of the nymphskin segments. Invert the vice, and now you’re ready to gill.

  Take two or three strands of organza (more can be applied if you want a bushy hydro). Where your thread is hanging, bring the organza under the thread and park it on the underside of the nymph. Tighten (you will notice that the organza is pulled into the nymphskin grooves). Repeat the process until you reach the thorax area, then tie in Veli Autie legs on the three remaining nymphskin segments. Whip finish and tie off. Snip off your thread then grab the trailing organza strands on the underside of the nymph and with curved scissors trim the organza to 2-3mm.

  Then with an olive Kurecolour pen stroke over the back of the nymph from eye to tail. Then get a black permanent marker and colour the thorax section.

  You have just completed a fairly realistic bug and a fantastic fishing fly

James Matthews, Ayr November 2004  ©