The Chernobyl Ant came out of the Green River in Utah in the early 1990s — the first big "junk dry" that admitted it wasn't trying to imitate anything in particular. Stacked foam layers (usually tan or black over yellow or red), rubber legs at the head and tail, sometimes an indicator wing.
It's the parent pattern of the modern attractor-foam universe: chubby chernobyls, hippie stompers, fat alberts, water walkers — all variations on the same theme.
Fish it on heavy 3X tippet (the fly bites are violent and the fish are usually big) in late summer through fall. Cast tight to the bank, twitch once on the landing to pop the legs, then dead-drift. Often the indicator dry for a heavy nymph dropper.