Queen catchers are small devices that consist of a plastic frame with a mesh or grid that allows worker bees to pass through while trapping the queen. Some queen catchers have a sliding door mechanism or plug that can be used to secure the queen inside the catcher once she's been captured. Adequate ventilation is essential when using a queen catcher to ensure the queen remains healthy and comfortable while confined. Some plastic queen catchers are designed with ventilation holes or mesh to allow airflow and prevent overheating.