Colloquial Terms: The Intrusion, the Hive, the Swarm, the Unseen Horseman, the Eighth Plague, PESTILENCE
Physical Characteristics: A swarm of animals of varying species, the only common trait is that each animal belongs to the phylum arthropoda (NOTE: See here --SΣ)
Behavioral Characteristics: A sort of consciousness that affects large groups of arthropods, causing them all to move with a single-minded purpose. Like the animals in their natural state, PRE16 seeks to reproduce. It does so by seeking out a human host. As the host sleeps, PRE16's bodies into into the host through each orifice and lay eggs within the host's body. The host begins to become ill as a result of that. Within a few days, the eggs hatch, and the offspring devour the host from within. PRE16, with its new bodies, proceeds to seek out a new victim.
Violence against individual bodies will only serve to agitate PRE16.
Further Reading: This blog