Blood-vein, Enderby Quarry 13th June 2004
This one is referable to f. nigra, and as far as I can gather it's pretty rare.
Dotted Border, Whetstone 17th April 2003
This is referable to f. fuscata, a fairly common form, but the only one I remember seeing that was this dark.
Lime Hawk-moth, Wicken Fen 18th May 2002
This is referable to f. brunnea, again the only one I remember seeing.
Brimstone Moth, Luffenham Heath Golf Course 14th June 2003
No idea if this is a named form, or a genuinely abberant individual, but certainly the only one I've ever seen.