Primal mutalisks are an everchanging breed, bearing many differences in their wings and tails. Some possess four wings and resemble wasps, while others have the solid wings similar to their Swarm counterparts. Some primal mutalisks develop subdued coloring in order to conceal themselves in many different environments.
In combat, primal mutalisks are identical to their normal counterparts in the Swarm, but do not benefit from the mutalisk's upgrades in the evolution pit. They also cannot evolve into brood lords or vipers.
Since the Primal Mutalisk cost 3 supply while 2 Primal Hydralisks cost 4, it is possible to free supply, especially when having reached the cap. 4 Primal Hydralisks merging thus could allow to gain 2 Primal Mutalisks, and rebuild 1 Primal Hydralisk.