Dust devils are a slayer monster which require the starting of Desert Treasure and 65 slayer to kill. Dust devils are good experience if you have the slayer to kill them and have an extremely good very rare drop, the Dragon Chainbody. The only other monster that drops this item is the Kalphite Queen, which is much harder to kill.
Note, however, that killing dust devils is much easier than killing the Kalphite Queen. Also note that, while dust devils are indeed easier to kill, the drop is much more rare.