Risen

The first moth encounter will be around the first ancient ruins you come across. There's 4 of them around the temple. The next encounter is probably the bandits camp in the Swamp. You will be tasked to clear out some insects during the quest Disgusting insects by way of Ricardo. Although it says Grave Moths, these insects count as the same. There are 4 of them on the small island in the swamp, netting you this achievement.