The Hydropsyche is very popular larvae from caddisflies family. Their abdomen occurs in various shades of green (in my local river this is nice chartreuse color), while the head is black.
You can tie easier version of the hydropsyche, in which should be omitted ostrich herl and tied in presented way legs, but then you have to comb black dubbing to imitate the legs of larvae.
Materials for Hydropsyche:
Hook: no. 10-12
Thread: UNI 8/0 black
Tail: white CdC
Body: Veniard Adhesive Lead Foil + green and black dubbing
Gills: Ostrich herl
Back: body stretch olive
Legs: 6 fibers of pheasant tail feather (painted on black)
Varnish: Veniard's black