Trichoniscus provisorius Racovitza, 1908

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 : 38

14. Trichoniscus provisorius Racovitza, 1908

( Fig. 11 h , Fig. 16 , Map 14 , Table 16)

More than 50% of the records are done in forest habitat ( Table 16). However, it is important to note that due to the close resemblance of T. provisorius and T. pusillus there was a need to collect larger numbers to assess the sex ratio of the population to get a confident identification (T. pusillus- populations have less than 1% males while this is more equal for T. provisoriuspopulations ) (see also DE SMEDT et al., 2020a). Abundances of these two species are generally higher in forest habitat and therefore this habitat was preferred to collect a sufficient number of individuals. Therefore, other habitats might be under-recorded, for instance gardens, parks, grasslands and river banks in open landscape. The species is (very) common in forest habitat, open landscape and anthropogenic habitat in the north-western part of the country ( Map 14 ). An absence in the Campine region, marked by quickly heating and acidic sandy soils, could possibly be due to a lower drought resistance of this species compared to T. pusillus since T. provisorius is on average smaller and has possibly the lowest desiccation resistance of all native woodlice species (see DIAS et al. (2013) based on the data from T. pusillus ). A lower resistance against acidic soil conditions may explain why the species is absent in the Ardenne and Lorraine region.

In all habitat types T. provisorius is more observed during winter months ( Fig. 16 ), however the period with highest number of records shifts slightly between different habitat types. Furthermore, it appears that the drop in corrected numbers of records during summer months is lower in forests compared to open landscape habitats. We assume this can be related to soil moisture conditions, which are more buffered in forests.

Figures

Map 14. Distribution map for Trichoniscus provisorius.

Fig. 11. a, Ligidium hypnorum; b, Androniscus dentiger; c, Haplophthalmus mengii; d, Hyloniscus riparius; e, Metatrichoniscoides leydigii; f, Trichoniscoides albidus; g, Trichoniscoides helveticus; h, Trichoniscus provisorius.

Fig. 16. Corrected number of observations per two-month period for Trichoniscus provisorius (N = 157).