Here are Dendrobium arachnites and Dendrobium unicum, very similar in growth habit, size and flower color, but unicum holds its flowers erect and rolls the sepals back while arachnites does not open as much and holds its flowers down. I cannot detect any scent with Dendrobium arachnites, but unicum has what is to me a very disagreeable scent, sweet but with a kind of chemical sharpness.
That unicum is wonderful!
How do you culture these Den's?
I grow the arachnites in a small pot in broken up tree fern and the unicum is on a treefern mount. They are both in with the Masdevallias and do well, though I think they will tolerate warmer temps.