Silicoid

The Silicoids (also known as The Swarm or Space Bees) are a hive of swarming alien drones found around planets. While very fast and well armed, the Silicoids don't seem to be very sturdy. Destroying their Hive is the best way to eliminate them as a threat. Provide a small income bonus when defeated.

They are not "alive" in the conventional sense. The silicoids are machines.

They were designed for mining, once upon a time. Apparently, the race that created them would build an automated way station in one asteroid — a depot which would build, fuel, and maintain the drones based on the ores that they delivered. The drones, armed with small cutting lasers, would go out into the field and tunnel into the rock, collect rich ore, returning it to the depot for refinement.

Whatever race created them abandoned the system eventually and left nothing behind but the silicoids. After years, decades, possible even centuries or millennia, the simple self–defense protocols of the mining depot and its drones have gone wild. Whereas once it was possible for their masters to broadcast a simple code to shut down the anti–theft measures, the drones now recognize no authority and berserkly attack anyone who enters their system. They are very aggressive, if clumsy, in their attempts to protect their "nest" — but if you destroy the depot, they "die", as they are no longer able to get fuel and maintenance from their "mother".

The beams for cutting are arrayed under the belly, and are relatively small and slow — not a weapons grade laser. They could not attack a moving ship able to defend itself with those, although they do descend rather quickly to chop up a derelict vessel and carry it back "home" when the crew has been killed.

The attack on live vessels is an ejection of plasma from the drone's minute engines. One of many reasons they "die" so quickly, if the nest is killed, is that they will have lost most of their fuel trying to fight off the attacker.