Only 2 will spawn on map at a time. Spawns are along the swamp River just south of the redwoods. Kill the males and take the pheromone from inventory(shotguns work well on them). When you find a female, have a tame nearby preferably a paracetamol for your first time. Damage the bug and peck at it with a low damage weapon to get below 10%. Put your tame on passive and feed it the pheromone. The rhynio will beat on it for a little bit but don't stress, it will fly up and whip down and impregnate your tame. (If you build a trap you can impregnate multiple tames, I've done 35 dinos off of 1 bug)

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