Mystery of the Pulsating Spider

In this video, what looks like a disembodied snake head is actually the carapace of a spider. Consider that a double trigger warning if you are terrified of watching either. It gets even weirder, though. Spider photographer Nicky Bay noticed something odd about a bird dropping spider he was watching. The spider's organs or fluid or something was moving underneath its skin! So he zoomed in and got a really close look. We don't know what the purpose for this is, but Bay has some theories. It could also be just normal digestion going on, but why would evolution make this so visible when most insects need to blend in with their background? (via Metafilter)