Scorpions have been doing quite nicely, thank you, since they left their yard-long ancestors in the sea 350 million years ago. Cannibals that also care for their young, they are found in caves at depths up to a half-mile, in deserts and high up on mountains. Biologists' discovery a generation ago that scorpions fluoresce under black (ultraviolet) light, and so can be easily seen and captured, has brought a golden age of scorpion studies. The good news is that only 25 or so of the 1,500 known species can kill a human being. The bad news is that they kill 800 people a year in Mexico alone. To get a closer look at this feared and fascinating creature, author John F. Ross accompanies scorpion experts Gary Polis and Philip Brownell on a specimen-hunting expedition in Mexico.