Oniscoidea

Abstract: Woodlice (Isopoda: Oniscoidea) are well defended by a heavy armour and many species have noxious secretions. Oniscophagy (feeding on woodlice) may be an important part of the biology of at least some members of the spider genus Dysdera (Dysderidae). Yet there little is known about the diet and possible specializations for feeding on woodlice in these spiders. Dysdera has unusual variability in mouthpart morphology, which may be related to the diet. Here, we investigate five species of Dysdera and consider the relationship between mouthpart morphology, capture frequency and prey-capture behaviour. We show that species with unmodified chelicerae readily capture a variety of arthropods, but refuse woodlice as prey, whereas species with modified chelicerae feed on woodlice and reject most of the other prey.

Abstract: SUMMARY The authors describe the zonation and activity of 12 species of Oniscoidea inhabiting the beach-dune-bush system and two found on the rocky coast at Sar Uanle (southern Somalia). The correlation between zonation and macro- and microclimate, the ecological affinities between these and other forms present on extra- and intertropical coasts, the tidal and diurnal rhythms involved in the migrations of Littorophiloscia compar (Budde-Lund) and the particular tree-dwelling bionomy of Periscyphis rubroantennatus Ferrara are also discussed.

Abstract: This study reports the species of five families of terrestrial isopod crustaceans (oniscoids) from Florida. Twelve species including three each of Tylos and Ligia and one each of Ligidium, Vandeloscia, Sayoscia, Rhyscotus, and a new genus, Floridoscia (with a new species), are included. Another common species from Florida. Philoscia floridana Van Name. is placed in a new genus, Ocelloscia. Illustrations, notes on habitat, and distribution maps are included for all 12 species.

Abstract: The results of field and laboratory investigations concerning the biology of Haloniscus searlei Chilton (Crustacea: Isopoda: Oniscoidea) are reported and discussed. It occurs in Victoria, Tasmania, South Australia, and Western Australia, where, although belonging to the almost exclusively terrestrial Oniscidae, it lives only in inland salt lakes; from these it has been collected at salinities from 8 to 159‰. Breeding females occur throughout the year, but are most abundant in summer. The life-cycle conforms to the typical isopodan pattern. Laboratory investigations provided upper and lower L.D.50 values for salinity with acclimation of 159 and < 1‰ and without acclimation of 118 and 4‰. In resistance to desiccation, H. searlei does not seem to be significantly different from terrestrial isopods, and in air its survival is a matter of hours. Its degree of cuticular impermeability places it between Oniscus and Porcellio in the following series of genera with increasing impermeability: Ligia < Philoscia < Oniscus < Haloniscus < Porcellio < Armadillidium. The pleopods display no modifications for terrestrial breathing. The view that H. searlei is of terrestrial ancestry and that its forbears were physiologically preadapted for life in inland salt lakes is upheld.