First natural glider
The first natural glider is the first glider released by a Herschel, named for being the first naturally occurring glider that was observed in the early days of Life research (by Conway's group when tracking the evolution of the R-pentomino). It is the main limiting factor in Herschel track compression. An eater5 variant is the method of choice for the deletion, but some new sparkers might be able to "reach in" and delete the glider faster than the eater5.
Likewise, the term "first natural block" refers to the first block that a Herschel produces. Most conduits use an eater 1 to remove it. Eater 1 can also eat a block predecessor, changing the Herschel's evolution.
First natural gliders are shot by the Simkin glider gun.