The Blood Suckler and its cousin the Bone Suckler are both kamikaze Suckler ANMCs, meaning that they self destruct when they get too close or die, which is when they get shot. Since their explosion can also damage other NMCs (for 60-70 damage on Normal/Replay), this can be useful in wiping out multiple groups of Sucklers or damaging Scorpions, Scavengers or Strangers that are in the vicinity.
While it is never shown in game, these are the children of the Mind Suckler and theoretically they could develop into the more advanced version.
