Here is a Nitro Caddis I found:
...at Deschutes Angler, in Olive
It looks remarkably like a pattern that was developed by Canadian tier, Jeremy Davies about eight years ago...he used ostrich herl for the collar/thorax...
PEARL CORE BRAID CADDIS PUPAE
Hook: TMC 2457, Diiachi 1120, # 14-16
Thread: Gordon Griffith’s 14/0 Black, Brown
Abdomen: Midge Pearl Core Braid, Olive, Tan, Black or Grey
Wing: Mottled partridge, Natural, Dyed brown or olive
Thorax: Black, brown or olive Ostrich Herl
Bead: Gold, Black
The Nitro Caddis appears to have a collar/thorax made from Olive/Brown Ice Dub...The pattern is from Umpqua so it should not be too difficult to get one's hands on it to de-construct...
Hope this helps !!!