...One important aspect of early work evaluating the relative crypsis of the forms of B. betularia on tree trunks with different lichen flora was the reliance on human observers. Humans, however, do not have the same visual capabilities as birds. Birds have well-developed ultraviolet (UV) vision, an important component of their colour processing system that affects many aspects of behaviour, including prey detection. We examined the UV characteristics of the two forms of B. betularia and a number of foliose and crustose lichens. In human visible light the speckled form typica appeared cyptic when seen against a background of foliose lichen, whereas the dark form carbonaria was conspicuous. Under UV light the situation was reversed. The foliose lichens absorbed UV and appeared dark as did carbonaria. Typica, however, reflected UV and was conspicuous. Against crustose lichens, typica was less visible than carbonaria in both visible and UV light. These findings are considered in relation to the distribution and recolonization of trees by lichens and the resting behaviour of B. betularia.
There have also been studies showing that these moths do rest on tree branches during the day, and that they preferentially choose resting locations where they camouflage well. I can provide citations if necessary.
Re: my response, bad as it was the first time and worse for repetition.
Why did darker moths increase wildly in population to 80% of the moth population in areas with no substantial industrial pollution?
That's misleading. Your quote actually says that the melanics "reached a frequency of 80%," without giving any indication of the degree to which this percentage differs from expectation. In fact, Lees and Creed state in that 1975 study that the increases and decreases at the individual study sites weren't statistically significant individually, but when the data were pooled by region a significant result could be reported.
There are possible population-dynamics explanations, but I'm reluctant to go into them without finding studies to support them in this case.
So why so many random mutation during industrial revolution have led to melanic forms, but we did not found any random mutation (even before and after) that led to other colors as melanic ones? Were mutations during the period really random? If directed, would not be that case of melanic moths somehow falsify darwinism?
I expect that RAZD will have no trouble answering you, but I'll just put in that it's because variations in melanism are very common among insects (and in other animals, too - as I see WK has already beaten me to pointing out). It's not a matter of mutating to form a novel pigment, or to express it in very different regions of the body or wings. It's mostly a matter of changing the degree of saturation of a pigment that is already produced.