Environment and Morphological Variation of Mitopus morio (Fabr.) (Opiliones) in Norway

Abstract

The morphology of Mitopus morio was studied at twenty-five localities in Norway, 1971-77. Body length and leg lengths varied according to Bergmann's and Allen's rules. A combination of latitude, altitude and exposition could account for 72-80% of femur length variation, long legs being found at low latitude and altitude and on south-facing slopes. Long-term summer maxi- mum temperature alone could account for 50-81%. When the latter variable was held constant the partial correlation with the long-term summer precipitation was significant and positive. Shorter femurs were found in mature forest compared with a nearby clear- felled area. Significant variation in femur length was established in relation to trapping date and year within single localities. Corpus penis length was also negatively correlated with trapping date. The growth increment for femur length of the successive ecdyses could closely be approximated by a second degree equation. According to the lengths of corpus penis and glans penis, the specimens