Porcellio dilatatus Brandt, 1833

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 : 70

29. Porcellio dilatatus Brandt, 1833

( Fig. 2 g , Fig. 33 , Map 29 , Table 31)

Porcellio dilatatus has only been recorded in anthropogenic habitats or in open landscape in places with clear human influence ( Table 31). Records of the species in gardens and parks concern mostly only one or a few individuals whereas in stables and barns on farms P. dilatatus is regularly observed in high numbers. Since P. dilatatus is a thermophilic species, we assume that constant warm and moist conditions in stables and barns are the optimal climate for a thriving population. Due to the continuing disappearance of old, small-scale farms the species is declining in Belgium ( DE SMEDT et al., 2020a). The species was not found under semi-natural conditions, which is the case in the south of the Netherlands, were the species is also known from calcareous grasslands ( BERG et al., 2008).

Due to the low number of records, it is difficult to draw conclusions based on the phenology diagram ( Fig. 33 ). The species is probably active year-round inside stables and barns on farms. Outside buildings, the species is rarer and probably inactive during winter months (personal observations).

Figures

Map 29. Distribution map for Porcellio dilatatus.

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. 33. Corrected number of observations per two-month period for Porcellio dilatatus (N = 18).