Darwin's bark spiders spin immensely tough silk into enormous webs across rivers and small lakes in Madagascar. Matjaž Gregorič at the Slovenian Academy of Sciences and Arts in Ljubljana and his colleagues report that the webs of this spider (Caerostris darwini) are the largest ever seen, with orbs spanning up to 2.76 square metres, and silk bridges as long as 25.5 metres. However, they might not be designed to catch large prey.

After filming webs for hundreds of hours, the researchers found no evidence that they trapped flying vertebrates such as birds, and in experiments the webs were unable to retain frogs or very large insects. These huge structures have unusually open architectures, and effectively provide large surfaces to catch semi-aquatic flying insects. Mass emergences of such creatures might provide an amount of food equivalent to a larger prey.

J. Arachnol. 39, 287–295 (2011)