 SCP-400 is the collective designation for an anomalous species of arthropod, similar to armadillidium vulgarae, or the common pill bug. SCP-400 is a parasitic organism, which feeds on human mammary secretions. Access to this food source is gained by habitation and manipulation of deceased human infants. Affected persons are subject to a type III cognitohazard via a pheromone vector, which repurposes the natural child-rearing instincts present in all humans for its own feeding and protection. Those subject to this effect are unable to perceive SCP-400, or the damage it causes to infants.