For me they are 1 of the most usefull tames since they can produce oil to power your generator without u having to go underwater with your sea shepperd (thats the must name for any marine creature) and also giving u great amiunts of fertilizer. I find that 3 dung beetles are already enough to power a generator constantly and still giving u enough oil for jerky. They also produce enough fertilizer for a few plant x species and a small greenhouse (theoretically u would have never to leave your base). U have to put them on wandering and they eat meat. U might wanna put them in a cage so they dont wander off. I recommend lvling up their weight so that u can put more poop in and dont have to care about them very often.
On Ab, there are no Phiomias, so here's an alternative: If you go into the red mushrooms, you will poop... A lot. You can load all that poop on a dung beatle and get lots of fertilizer! It will give you more for bigger poop though.