"I Vant' To Suck Your Blood" Vampires? Nope. Bed Bugs.

Bed bugs are blood feeders.  Bed bugs only consume blood, usually feeding on a mammal (e.g., human, bat) or bird.
They need at least one blood meal of adequate volume in each active life stage (instar) to develop to the next stage and to reproduce.
There are five nymphal stages, and each one may feed multiple times if hosts are readily available.