I was being a little facetious, saying the Taxxons are comprised of dirt, sort of like saying a sailor is made of the surf or...never mind I really don't want to defend that.
And yeah, if you ate a koala it wouldn't taste like eucalyptus leaves, and I don't know if any cannibals frequent this forum but certainly humans don't taste like chocolate and hamburgers and potato chips. But what the things we eat themselves eat is often a matter of concern and quality. Corn-fed beef, for instance. But I guess what I was thinking of was more along the lines of growing a garden and irrigating it with well water--when you eat the vegetables, they taste like iron. And the Taxxons just happen to be a race whose main, if not only, source of sustenance tastes like iron, are addicted to iron, and have evolved not only to eat it but to eat it constantly as a source of their instinctual urge to dig. So if, by some magical, soft sci-fi process, "The Living Hive" contrives Taxxons from the magically nutrient-enriched Taxxon earth, maybe they will taste like dirt. And would be delicious to a Taxxon. It's as good a theory in any, imho, because I agree that the law of conservation of matter and energy pretty much dictates that the Taxxon race will die out if they are exclusively cannibalistic.
I hope this makes sense. Now I want to write a fic about the process by which the Living Hive spawns Taxxons...