The Scornet is a member of the Unknown Family in Pikmin 3. It is a small cone shaped hornet-like creature that is fought in swarm and fufil the role of a worker while the Scornet Maestro fufil the role of the "queen".
When found in a swarm without a Scornet Maestro, they will be uncoordinated and try to grab Pikmin. After a while, they will kill them. The captains can throw Pikmin at the scornets to kill them before they kill the Pikmin that they hold hostage. When a Scornet Maestro is with them, they will adopt battle formations and become way more efficient.