A device for the prevention of entry of flying and non-flying stinging insects into open disposable beverage containers. At low revolutions per minute, the stepping motor offers higher torque as compared with the known DC motors, whereas it also offers high revolutions per minute, although with comparatively low torque, sufficient for rapid advance and retraction of the plungers. The memory sheet has silicon chips for memory. The winder enables a user to pre-determine the dimension of cable length and cable efficiency in order to maximize operation effectiveness. ROM chips can be swapped to allow the fluorometer to be configured and reconfigured to perform a plurality of different tests. A distal end of the resilient hook is releasably received in the opening and abuts a peripheral wall of the opening.