The Black Beetle is a rare NMC. They can be very dangerous, do deal good damage and approach Aya, quickly. They also have insanely high defense which prevents them from taking much damage from most attacks. Buckshot and Electrical attacks like Apobiosis and Plasma can knock them over, allowing Aya to attack their underside, which allow you to deal much more damage. The targeting system is a bit of an issue against them, so be careful. After a while, they will flip back over and need to be knocked back again.
The Beetle's attack is based on how much running time it has before making contact with Aya, with the minimum damage being 1/3 of what has been listed. On the plus side, Beetles attack in a straight line (much like the Chaser), meaning it is possible to side-step an incoming attack.