Ecology and body size of the parthenogenetic Megabunus diadema (Fabricius, 1779) (Opiliones: Phalangiidae) at Karmøy, Western Norway

The presently known distribution of Megabunus diadema is summarized and presented as a map. The species is known from Iceland, the Faroe Islands, Western Norway, Great Britain, Western France by the English Channel and Northern Spain. M. diadema was studied in 9 localities at the island of RY Karmøy, Ryfylke (EIS 13) in Western Norway from 3 different biotopes during the period of 15 June - 10 July 1997. During this period, 261 females and 3 males were collected by hand-picking. M. diadema is mainly a parthenogenetic species, and these males are the first reported from Norway. Regarding morphological characters the body length, movable cheliceral finger, pedipalpal tarsus and 1. eye spine were measured. Both the smallest and largest body length were found in specimens from coniferous wood. Compared to Western Europe and Great Britain no geographical differences were detected regarding body length. Regarding movable cheliceral finger length specimens from different coniferous woods were both smallest and largest in size. The length of pedipalpal tarsus was smallest in mixed wood and greatest in coniferous wood. 1. eye spine length was smallest in mixed wood and largest in coniferous wood. The southern distribution limit of M. diadema was found to lie close to the county border of VAY Vest-Agder. The biotope preference of the species was found to be mixed wood, and the density maximum was in the last week of June.