Lecidea fuscoatra
When looking at a lichen that looks just like a million other lichens to the naked eye, how are you supposed to tell them apart? Spot testing! Spot testing involves using chemicals dropped onto sections of the thallus and observing any color changing reaction. The three diluted chemical solutions most commonly used contain potassium hydroxide (K-test), calcium hypochlorite/bleach (C-test), and para-phenylenediamine (P-test). You can also do a KC test with a drop of K solution followed by a drop of C. Here’s what L. fuscoatra looks like following C, K, and KC spot tests:
Pretty distinctive color change, right? Well that C positive reaction, K negative reaction, and KC positive reaction is indicative of the species, and helps to discern it from look-alikes like Miriquidica deusta and Immersaria athroocarpa which display no reaction to C or K. Pretty neat, huh?
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