I sent a copy of J. Haynes' recent letter, about the encounter with black rattlesnakes, to my biologist son, James Valade. I think his comments may be of interest to your readers:
"While there are species of black or darkly colored rattlesnakes, chances are pretty good that this (was) a melanistic rattlesnake. Melanistic rattlesnakes are the result of a recessive genetic trait, similar to albinism in humans. Instead of being a normal color (or white, as in the case of albinism), this one was black.
"If the rattlesnake that was killed earlier was also black, that wouldn't be too surprising, given the fact that there was already at least one black rattlesnake in the neighborhood. Where you have-the expression of a recessive trait in an individual, it's not uncommon to see similar individuals, perhaps from the same clutch, in the same locale.
"In regards to the observation that "if you kill a rattlesnake, another will show up in the same place soon after," there's some truth to that observation, although chances are pretty good that it is not the dead snake's mate.
"Snakes roam over extensive areas and have an excellent sense of smell. The scent of another snake, especially that of a dead one, would be of interest to another snake, as would be productive paths where game can be easily found."