What is "epicuticles"

Usage examples of "epicuticles".

And sometimes, on clouded nights when there wasn't even much starshine to guide them, went out scogger-hunting in the velvet dark (stumbling over bushes and hillocks, with ultraviolet lights that made the grubs' epicuticles fluoresce so they looked like neon-lit cockroaches in the night) and broiled their catch for breakfast.