Haplophthalmus danicus Budde-Lund, 1880

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 : 18

4. Haplophthalmus danicus Budde-Lund, 1880

( Fig. 2 b , Fig. 6 , Map 5 , Table 7)

A small species occurring in a wide range of habitats ( Table 7) and more common in the northern part of the country ( Map 5 ). The species is common as well on the sandy soils in the Campine region in contrast to most other species. In the south, the species is absent from open landscape habitat. The species is mostly found in the humus layer or in decaying wood or other organic material and this results in more than 50% of the records located in forest habitats ( Table 7). In anthropogenic habitat, H. danicus occurs commonly in gardens and parks, where compost heaps are favoured.

In both anthropogenic and forest habitats, H. danicus is more commonly found during winter months ( Fig. 6 ) (see also DE SMEDT et al., 2021). This pattern is less clear in open landscapes, possibly due to the limited number of records in this habitat. Despite being more commonly found in colder months, the species is less common in southern Belgium, where average temperatures are lower throughout the year. This could indicate a low tolerance for low temperatures. H. danicus is a drought-sensitive species ( DIAS et al., 2013) and we can assume that the lower humidity during summer months causes a decrease in observations because the species retreats deeper into the soil.

Figures

Map 5. Distribution map for Haplophthalmus danicus.

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. 6. Corrected number of observations per two-month period for Haplophthalmus danicus (N = 163).