Caerostris darwini was described in 2010 from Madagascar, where its webs were found hanging over rivers rather than among vegetation. The bridging line that spans the water may reach twenty-five metres, and the orb hung beneath it has been measured at up to roughly 2.8 square metres, the largest orb web recorded.
The silk matches the ambition. Laboratory testing of the dragline gave a toughness of around 350 megajoules per cubic metre, about twice that measured for other spider silks and an order of magnitude above high-performance synthetic fibres of comparable strength. The web must absorb the impact of insects arriving over open water without an intervening branch to share the load.
The spider's take is correspondingly unusual. Webs suspended over a river intercept mayflies and other emerging aquatic insects, and dozens have been recorded in a single web at once.