Natural Plastics for Defense

The beetle, Abax ater, secretes monomeric methyl methacrylate. This material instantly polymerizes, immobilizing the beetle's enemies by encasing them in what is essentially chemically identical to plexiglass.

The first plastic invented by humans was cellulose nitrate, the formulation of which was discovered by accident in a chemist's kitchen. The ivory market was one of the first to be displaced, celluloid being an easy replacement for everything from knife handles to billiard balls. Being highly combustible--and explosive with a forceful strike-- these early plastic billiard balls occasionally exploded upon being hit by a pool player's cue.

"Three ball in the corner pocket..." BANG!

I reckon this had the general effect of increasing the number of gun fights in the Old West.