It emits carbon dioxide (the same gas people expel during respiration) that is generated when ultraviolet rays from the internal fluorescent bulbs react with a titanium dioxide coating inside the trap.
In addition to mosquitoes, it catches biting flies, house flies, sand flies, blow flies, drain flies, moths, no-see-ums, June beetles, wasps, yellow jackets, stink bugs, gnats, and biting midges.) The carbon dioxide and warm UV light in this outdoor mosquito trap lures mosquitoes to the trap and an integrated fan traps them in a removable compartment where they die of dehydration. 46 1/2 H x 12 1/2 Diam. Half Acre Decorative Mosquito Trap | Outdoor Pest Control by Hammacher Schlemmer with stand.