Wantsen van de Nederlandse Waddeneilanden II (Hemiptera: Heteroptera)

Bugs of the West Frisian Islands ii (Hemiptera: Heteroptera) The first review of Heteroptera recorded from the West Frisian Islands was published in 1989 and included records of 278 species. To date, our knowledge of the fauna of these islands increased considerably, resulting in records of 336 species and 351 new island records. Texel houses most species since 2004 (279 against 181 in 1989), finally outnumbering Terschelling (272 against 240 in 1989) and also the numbers of known species from Ameland, Schiermonnikoog and Vlieland increased considerably. A review is given of all new island records since 1989 and a number of especially interesting species is treated in more detail. Comparisons are made between the fauna of the West Frisian Islands and that of the nearby mainland (provinces of Noord-Holland (the northern part only), Friesland and Groningen) and of the German East and North Frisian Islands. The distribution of Lygocoris minor (Miridae) is limited to the Dutch and German Frisian Islands, and Orius horvathi (Anthocoridae), Kleidocerys ericae (Lygaeidae) and Piesma salsolae (Piesmatidae) in The Netherlands only are known from the West Frisian Islands and do not occur on the German Islands. Orius horvathi is recorded here for the first time from the Netherlands. The five largest West Frisian Islands have only 105 of the 336 known species in common and there are large differences in species composition between the islands. Texel and Terschelling show the highest resemblance with 70,0 percent of the species in common, whereas for the other islands this percentage varies between 49,2 and 58,8. A total of 63 species were recorded on a single islands only, most of them on Texel (31 species) and Terschelling (20). Almost all species of the West Frisian Islands (91,1%) also occur on the nearby mainland, but 109 species known from this part of the mainland were never found on the West Frisian Islands. The resemblance with the northern part of North-Holland is the largest (67,3%), followed by Friesland (64,2%) and Groningen (57,3%), respectively. Based on the presence of flightless species on the islands and the fast colonization of the islands by a number of invasive species, it is supposed that the absence of species likely to occur depends on other factors than just isolation from the mainland.