Trichoniscus pygmaeus Sars, 1898

Boeraeve, Pepijn, Arijs, Gert, Segers, Stijn, Smedt, Pallieter De, Spinicornis & Utm, Belgium. Every grid cell of the, 1908, Habitat and seasonal activity patterns of the terrestrial isopods (Isopoda: Oniscidea) of Belgium, Belgian Journal of Entomology 116, pp. 1-95 : 42

16. Trichoniscus pygmaeus Sars, 1898

( Fig. 2 d , Fig. 18 , Map 16 , Table 18)

Trichoniscus pygmaeus is found in a wide range of habitats ( Table 18). In the northern part of the country, the species is less common and rare ( Map 16 ). In Southern Belgium, T. pygmaeus is almost exclusively found in anthropogenic habitats. In the other parts, the species is more common and forests are an important habitat for the species. Forests consist of almost 50% of the records and half of it are near water in forests ( Table 18). In anthropogenic habitats only a limited number of records (6.9%) is near water, most records (65.5%) are from graveyards. The largest share of observations of T. pygmaeus in open landscape (66.7%) is located near water. Moist conditions in open landscape are probably only relatively stable close to stream- and riverbanks ensuring suitable habitat year-round for this soil-dwelling species.

In line with other small, soil-dwelling species, T. pygmaeus is less commonly found during summer months ( Fig. 18 ). This pattern is particularly obvious in anthropogenic and forest habitat, but less pronounced in open landscape habitat, although this habitat type has the lowest number of records. The patterns of T. pygmaeus in open landscape are comparable to the patterns in open landscape for T. pusillus .

Figures

Map 16. Distribution map for Trichoniscus pygmaeus.

Fig. 2. a, Ligia oceanica; b, Haplophthalmus danicus; c, Miktoniscus patience; d, Trichoniscus pygmaeus; e, Armadillidium pictum; f, Armadillidium vulgare; g, Porcellio dilatatus; h, Porcellio laevis.

Fig. 18. Corrected number of observations per two-month period for Trichoniscus pygmaeus (N = 162).