Flatworm caught hunting and killing spider on its own web

A ravenous flatworm is such a dangerous predator that it can even attack and kill a spider perched on its web, a first-of-its-kind observation shows.

In February 2014, João Cardoso – now at the Federal University of Uberlândia in Brazil – was a master’s student spending 15 days in Brazil’s Atlantic Forest conducting research on spiders. One afternoon along the Mirante River, Cardoso came across the web of a comb-footed spider (Helvibis longicauda) …