Skraal was able to stop the Red Acid Ants from hunting down his Ethereal Winged Snake by ordering the Snakes to cast ghost energy shields.
But this also blocks Ethereal Winged Snakes from attacking Black Ants on the ground or destroying Red Acid Ants, which pose a threat to themselves.
Using ghost energy shields stops them from giving more energy to attack capability.
They cannot do the same thing at the same time. They cannot shoot down on the ground and cast a shield to defend themselves at the same time.
Skraal knew that if he were to enter the battle himself, he could easily destroy all the ants or Red Acid Ants attacking their troops, but he was not going to do that.
In a sense, these kinds of things are not always good for him. He needs to improve his battle tactics and experience, not just destroy enemies with overwhelming force.