The only wild one I have found was in the island swamp, I have heard people saying they are on lost island also. To get them you need to kill one and take the special item it drops, then you need to find the one you want to tame and get it below 10% health like a reaper, then feed the special item to a sacrifice dino and eventually the bug will lay its eggs in it, make sure your Dino can eat the special item first as there seem to be some restrictions. you need to feed the Dino with the eggs something special every once in a while like a imprint and eventually it hatches and kills your Dino and you can claim the baby and raise it.

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