I think that Reader's theory of axehounds makes sense. The largest contributing factor to me is the antennae- they're exactly the same in both the notebook illustration and cover art. I agree on the six legs and mandibles point, and the tails could be seen as either a stinger-like abdomen or the shrimp-like structure from the notebook, depending on your point of view. However, there are still the wings, claws, and different head structure to explain. To this end I suggest a slight deviation-
Could it be that Selay axehounds fly? It's a bit of a stretch, but given the comparison- dependent parshmen to fully intelligent Parshendi- it allows a fair amount of leeway.
To be honest, I'd prefer them to be almighty crabdragons/crabwasps. With or without gemheart-fueled firebreathing capabilities. Despite that, my logical half still says flying axehounds.