Letterboxer

In the US, letterboxes have developed new forms: ; Cootie : Much like a hitchhiker, except instead of being carried from letterbox to letterbox, a letterboxer passes it to another letterboxer.

Normally, there are at least one or two hitchhikers in the box at all times, and any letterboxer who takes a hitchhiker out is required to leave a new one in its place.

The letterboxer that has done the moving also has the choice of sending the parasite along with a different hitchhiker.

When a letterboxer joins a parasite to a hitchhiker ("infecting" it), it is stamped into the hitchhiker.