Sandy
The dressing in St Headley's book, attributed to Bert sharp
Hook: Partridge L3A Size 14,16
Silk : Black
Tag : two turns narrow flat silver
Body : tying silk
Wing : paired slips of magpie tail tied low over the body
Hackle : one or two turns of black hen in front of the wing
The photo shows a black spider with a wing of about 3 times the body length.
A similar pattern is suggested for night fishing but in larger sizes with a peacock herl body and more turns of hackle.
Hope this helps
Irvine