As part of YouTube Geek Week, the Ri and Dr Tim Cockerill explore the science of Leeches.
As an entomologist, Tim is used to getting up close and personal with insects and here he lets a hungry leech feed on his arm - all in the name of science.
By observing the feeding process (for over three hours!), Tim explores the science behind how leeches live, thrive and survive and challenges some popular misconceptions along the way.
Warning: contains footage of blood.