In the "Flesh Guide for Hatchlings" in the dragon guild in Scorn, it says that scorpion's stinger is good food. However they are now poison rather than tasty for dragons. In general, it would be good to update the guides with foods that currently provide the different resistances, I do not currently know of any low level foods that give resist poison or resist fire the way that zombie corpses and ogre parts give resist cold and electric.
Are the guild books incorrect about scorpion stingers or are the stingers "bugged" and do not work as dragon food?
Good question, either answer could be correct depending on who is looking at it. I think that ideal would be for a new insect body part(thorax or claw maybe, people eat lobster claws after all) to be added that makes sense as food to provide poison resist, and the stingers stay as an alchemy ingredient and maybe a weapon. Of course that would need new artwork and updates to some treasure lists, so it's significantly more work. If someone had the time and art skills, there are a lot of things that would make sense to drop body parts that do not currently.