The 40-watt black light bulb increases catch by over 40% than traditional ultraviolet white light bulbs. The Octenol lure helps attract mosquitoes and other blood seeking insects by emitting a sent similar to a large mammal. To help save energy the Ultra Bug Zapper showcases a sundown sensor that turns off the zapper during the day when there are no mosquitoes. An easy to see indicator switch lets you know when the zapper is working.