02624nas a2200229   4500008004100000245007300041210006900114300001200183490000700195520194600202653001402148653001602162653002302178653002102201653001502222653002502237653002002262653002702282100001502309700001702324856005302341       2010                        eng d00aWeb gigantism in Darwin's bark spider, a new species from Madagascar0 aWeb gigantism in Darwins bark spider a new species from Madagasc  a346-3560 v383 a<p>The remarkable bark spiders (genus Caerostris: Araneidae) are poorly known Old World tropical orb-weavers, those diversity, currently at 11 species, is grossly underestimated. Most species build large webs at forest edges, clearings, and gardens, but in Madagascar, probably the hot spot of Caerostris diversity, at least one species occupies a unique ecological niche: casting its web across streams, rivers and lakes, so that the orb is suspended above water and attached to substrate on each riverbank via bridgelines up to 25 m. Here, we summarize current knowledge on Caerostris natural history, and specifically focus on the remarkable web architecture and biology of the newly described Caerostris darwini n. sp. Darwin&rsquo;s bark spider builds its web, a regular orb suspended above water, and maintains it with daily reinforcing of bridgelines and renewal of orb for many days. Web size ranged from 900&ndash;28,000 cm2, with the largest measured web of about 2.8 m2 being the largest orb ever measured, to our knowledge. With anchor lines capable of bridging over 25 m, it also builds the longest webs among all spiders&mdash;a unique form of web gigantism. We report on mass capture of ephemeropteran prey items in C. darwini n. sp. webs during a single day. Webs contained up to 32 mayflies that were subsequently wrapped en masse before the spider fed on them. We also provide the first evidence of kleptoparasitism in these webs both by other spiders (Argyrodinae) and by newly documented, undescribed symbiotic flies. Caerostris display extreme sexual size dimorphism with large females and small males, which is manifested in enigmatic sexual behaviors such as mate guarding, male-male aggressiveness, genital mutilation, mate plugging, and self castration. Caerostris is thus a promising candidate for evolutionary studies, and its diversity, biology, and phylogenetic relationships all deserve a closer scrutiny.</p>
10aDiversity10aDNA barcode10agenital mutilation10akleptoparasitism10amorphology10aorb web architecture10asexual behavior10asexual size dimorphism1 aKuntner, M1 aAgnarsson, I  uhttp://www.bioone.org/doi/full/10.1636/B09-113.1