Centipedes are arthropods with many leg bearing segments that vary from 15 to 191 segments in mature adults. Out of thousands of species, none (zero!) have an even number of segments when they are mature. All have an odd number of leg bearing segments. Biologists have puzzled over this odd observation trying to find explanations for this phenomena.
Immature centipedes exist that have an even number of segments and they are perfectly viable. Still, natural selection does…
Source: Living With Insects Blog