A bulbmin or Parasiticus pikminicus is literally a pikmin that looks like a bulborb because a parasitic pikmin has infected it. They can only be found in the sublevels of some caves and you need 1-10 free pikmin slots in order for the mature bulbmin to have younger ones following it. When you exterminate the older bulbmin, the small ones go into a panic and when you whistle at them, they are now under your command. They can be changed into other pikmin via candypopbud species, and they are also immune to all hazards (fire, water, electricity, and poison; excluding explosions). As good as their abilities may seem, they cannot leave the caves with you, so it would be best to change them if possible. The only way they could be killed if they are not under your command is if an armored cannon beetle relative flattens them, or a glitch occurs in the cave walls and they 'fall' in (though unfathomably impossible) if they a shaken by enemy attack and/or explosion, etc. The most populated place where you may find these is the Submerged Castle. Also, if you don't have the bulbmin under your command,and you have 90 or more Pikmin already, and you use Queen Candypop Buds, no Pikmin will pop out because of the bulbmins' presence.