Make a 2x2 stone trap 2 walls high with a ramp, lure the mantis in and replace any piece of the trap the mantis is aggrod on. When it's calm you can feed it your horns through the wall without guille or bug repellant

Can be tamed with rhino horns at reduced taming efficiency.

Best place to gather deathworm horns is the ice dungeon on ragnarok.