|A Centipede. A Centipede has one pair of legs per
body segment, whereas the similar millipede has two pair of legs
per body segment. According to Wikipedia, there are about 3,000 species
that have been described and identified, and probably another 5,000 species.
The first picture was taken 1 April 2008 in Colorado Springs, CO.
It was less than 3/4" long. When I first looked at the centipede in the first
picture, I thought it was a Millipede, since I could count twice the number of leg
pairs as body segments.
But once I looked at some other centipedes, as in the second picture taken 4 August 2008, I could see that they have mostly alternating wide and narrow body segments, and counted that way, they have one leg pair per body segment, therefore they are centipedes, not millipedes.
Having 15 body segments with 15 pairs of legs pretty well narrows it down to the Genus Lithobius, but there are over 300 species within that Genus.