That looks just like the dark stains from the bore holes and an opened-up chamber of those flat-headed wood grubs. There was a time when I didn't recognize the signs and ignored them, as dark anomalies in Osage, but then I felled a tree with heavy damage and realized what I was looking at. And while Osage can have dark rings in it, that dark stripe on the edge of the bow can be the tree ring reacting downstream from the grub's injury to the tree.
I decided to waste my time and follow the trails of damage, trying to cut-out the damaged areas until I was satisfied that I'd chased the holes to dead ends. -And several times, that ended with finding the live grub - still alive and eating, after the log had been seasoning in a hot shed for 9 months. But I would slowly chisel out the bore holes (running inward from bark to heart, just like how a nail is driven into a tree), then I found they'd stop at a tasty ring they liked and stay in it, eating lengthwise with the trunk. Then I'd often find the grub in an eaten-out chamber at the end of that tunnel. And that chamber will stain the ring below and the rind above with that dark brownish-red cloud. Then you see that stain streaking out downstream for a bit. NOT saying that's what you've got there - just had to throw it out.