ALBERT

Description: Bugs of the West Frisian Islands ii (Hemiptera: Heteroptera)\nThe first review of Heteroptera recorded from the West Frisian Islands was published in 1989\nand included records of 278 species. To date, our knowledge of the fauna of these islands increased\nconsiderably, resulting in records of 336 species and 351 new island records. Texel houses\nmost species since 2004 (279 against 181 in 1989), finally outnumbering Terschelling (272 against\n240 in 1989) and also the numbers of known species from Ameland, Schiermonnikoog and\nVlieland increased considerably. A review is given of all new island records since 1989 and a\nnumber of especially interesting species is treated in more detail. Comparisons are made\nbetween the fauna of the West Frisian Islands and that of the nearby mainland (provinces of\nNoord-Holland (the northern part only), Friesland and Groningen) and of the German East\nand North Frisian Islands.\nThe distribution of Lygocoris minor (Miridae) is limited to the Dutch and German Frisian\nIslands, and Orius horvathi (Anthocoridae), Kleidocerys ericae (Lygaeidae) and Piesma salsolae\n(Piesmatidae) in The Netherlands only are known from the West Frisian Islands and do not\noccur on the German Islands. Orius horvathi is recorded here for the first time from the\nNetherlands. The five largest West Frisian Islands have only 105 of the 336 known species in\ncommon and there are large differences in species composition between the islands. Texel and\nTerschelling show the highest resemblance with 70,0 percent of the species in common,\nwhereas for the other islands this percentage varies between 49,2 and 58,8. A total of 63\nspecies were recorded on a single islands only, most of them on Texel (31 species) and\nTerschelling (20).\nAlmost all species of the West Frisian Islands (91,1%) also occur on the nearby mainland, but\n109 species known from this part of the mainland were never found on the West Frisian\nIslands. The resemblance with the northern part of North-Holland is the largest (67,3%),\nfollowed by Friesland (64,2%) and Groningen (57,3%), respectively.\nBased on the presence of flightless species on the islands and the fast colonization of the\nislands by a number of invasive species, it is supposed that the absence of species likely to\noccur depends on other factors than just isolation from the mainland.