G rank Altaroths (sp?) The yellow bugs that crawl on the ground. You have to kill them without making them burst, preferably with poison smoke bombs or a weak poison weapon. For more detail, just use the search function. I'm sure someone's gone into detail about the best place to farm em... Maybe Misty Peaks?
PSN - The_Daiyu 3DS - Monster Hunter 3 Ultimate, Fire Emblem Awakening, and Animal Crossing: A New Leaf (1435-3945-2362)
I've obtained all the prized stomachs I needed by using the 'Hunters for Hire' doing G rank small monsters quests. If you have any, I suggest sending them on that. There's a quest specifically to kill altaroths or something along those lines.. Also receive bnahabra parts too.