In the invert forum there's a post, I think, linked to a video of a fascinating insect larval form, that is sucking a bloodworm dry.
The photography is brilliant, you can see the bloodworm's mouth parts and segments, see the juices running through the larval body very clearly, and the 'blood' leaving the bloodworm, segment by segment. A bit graphic but interesting. I'll see if I can find it again.
Edit.. this is the link to the video.