Morphometrics and SEM analysis of the species pair Lithobius mutabilis L. Koch, 1862 and L. glacialis Verhoeff, 1937 (Chilopoda: Lithobiomorpha)

The sets of morphological characters of two nominal species in the genus Lithobius Leach, 1814, Lithobius mutabilis L. Koch, 1862 and Lithobius glacialis Verhoeff, 1937, were studied in order to test specific dissimilarity. Morphometrics were examined and analysed statistically. In addition, a comparative SEM analysis of external characters was made. Morphometrically significant differences between the species were found concerning body length, the width ratio of the head to the 5th tergite, the number of antennal articles, and the length/width proportions of certain articles (e.g. the femur) of the 15th legs of males. Because of these and several additional differences, such as in tergite surface structure, modifications to the 15th legs of males, the structure of the female gonopod claws, and between the ecological profiles, L. glacialis, which is found in the high Alps at altitudes above timberline (1300 m), can be distinguished clearly from L. mutabilis. This study demonstrates another example for a cryptic species pair, a common phenomenon between lowland and alpine populations of small invertebrates. The combination of morphometrics and SEM offers a powerful methodology for resolving previously uncertain questions in the species-level taxonomy of centipedes.