if you are trying to get eggs, they need to be left on areas of the map marked as “wilderness”. on the island its herb island. on ragnarok its the area by the hidden scar where the sand and grass meet.
The most versatile of Scorched Earths creatures. A Mantis can hold the roles of multiple different creatures depending on the tools or weapons it has equipped. Picks and Hatchets make them ultimate harvesters, Pikes and Swords can turn them into deadly combat mounts and Clubs can allow them to quickly down creatures for taming, they have no need for Sickles since they can harvest fiber by default. However you'll need to level it's stats depending on the role you plan to assign it to. For example, if you want too make a Mantis a harvester weight and Melee are what you'll want to go for, if you want it to be a expert at combat health and Melee with some stamina in case things go wrong and you have to flee are the way to go since there pounce attack is enough to quickly cover ground and escape a aggressor, and KO'ers really need nothing more then health in case the target is something strong that fights back and some Melee to increase the amount of torpor inflicted by the clubs
If you are taming these for their Eggs, make sure to place them in an area that's "Unknown" (changed to "Wilderness" in recent patch). It'll quadruple your Egg harvest. Just leave render range for 5-10 minuted, come back and collect your eggs. They can also be egg-boosted by a Oviraptor now so make sure one is in range.