Biological peculiarities of the woodlouse Trachelipus rathkii (Isopoda, Oniscidea) in biotopes of the city of Kaluga

摘要

The spatial and temporal distribution of the woodlouse Trachelipus rathkii Brandt, 1833 (Trachelipodidae) was investigated using pitfall traps in various urban habitats. The species was found in all the examined sites but preferred habitats with patches of dense herbage: meadows around industrial objects, moist ravines, grassy yards, and gardens. In the mosaic gardens, woodlice preferred grassy areas and avoided cultivated microhabitats. The total sex ratio varied in different sites and years but almost everywhere the percentage of males decreased during summer. Gravid females occurred from June to August. The first peak of their abundance was mainly formed by large (old) woodlice, and the second, by small (young) ones. Females laid 7-106 eggs (on average 35.9). A strong positive correlation between the fecundity and body size of woodlice was observed. Two types of seasonal dynamics of the woodlouse activity were observed in the areas studied. In the first type, the local population had a seasonal peak of abundance which coincided with the maximum proportion of gravid females. These assemblages seem to be complete local populations occupying residential habitats. In the local assemblages of the second type the seasonal peak of abundance fell after the reproduction period. They seem to be incomplete local populations occupying transit habitats.