A device for subjecting a flying insect to lethal radiation. The device has a measurement beam source for producing a measurement beam, a deflection unit for deflecting the measurement beam, a lethal radiation source for producing a lethal beam and a measurement beam detector. The measurement detector has a photodetector element, the deflection unit and the measurement beam detector are arranged and cooperate such that the measurement beam sweeps the detector surface of the measurement beam detector. The device includes an evaluation unit connected to the measurement detector and the lethal light source to determine an attenuation time period of an attenuation of the measurement beam between the deflection unit and the detector surface and to control the lethal light source depending on said attenuation time to emit a lethal beam impulse. A method for subjecting a flying insect to lethal radiation is also provided.