Since in laboratory experiments a relationship between segment number and temperature in geophilomorph centipedes has been proven, we suggest that climatic variation in nature could have a direct effect on segment number. To address this hypothesis we examine the way in which local climatic factors in Sognefjord — air temperature and precipitation both changing along a longitudinal gradient — exert their effect on segment number in Geophilus flavus. Changes in G. flavus segment number along the climatic gradient are similar to that found in previous laboratory experiments with Strigamia maritima, but are even more pronounced. In G. flavus, a 1.5 difference in the mean segment number is found in populations that occur in Sognefjord along a temperature gradient of only about 1.4 °C. In contrast, several degrees centigrade were required to produce a similar increase in the mean segment number in laboratory experiments involving S. maritima.