What Insects Are Attracted To Lights At Night?

Few things pull pests toward a house as directly as an outdoor light, and few are as easy to fix. A porch light left on all night is calling insects straight to your doors, and those insects then bring in the animals that hunt them.

Which Insects Come To Light

Not every insect is drawn in, but the ones that are show up reliably.

Moths. The best-known example. Most moths that fly at night head straight for light.

Beetles. June beetles, ground beetles, darkling beetles, and click beetles all gather at lights. They are also the ones most likely to wind up inside, because they land, crawl along the ground, and slip under doors.

Gnats, midges, and small flies. These arrive in the biggest numbers, especially near water, which here means pools, golf course ponds, and anywhere near the Virgin River or Santa Clara River.

Mosquitoes and other insects bred in standing water. Washes, ponds, and irrigation runoff produce them in waves, especially after monsoon storms.

Leafhoppers. Tiny, numerous, and often mistaken for gnats.

Lacewings. Helpful predators, but they come to lights and find their way in.

Crickets. Field crickets swarm lights in late summer and fall in southern Utah and pile up around doors and garage seals.

Winged ants and termites. The reproductive swarmers, especially during mating flights after warm rains.

Not drawn to light: cockroaches, which avoid it, and most spiders and scorpions, which show up for a different reason.

Why It Happens

Scientists still debate the details, but the leading idea is that night-flying insects steer by keeping a faraway light, like the moon, at a steady angle. A light close by breaks that system. Holding a steady angle to a nearby source sends the insect spiraling inward, which is why they circle a bulb instead of flying straight at it.

Other factors pile on. Many insects are especially drawn to ultraviolet light, and some may read a bright light as open sky and fly toward it to escape.

The Second-Order Problem

For pest control, this is the part that matters.

Lights gather insects, and gathered insects attract predators. Within days of a new light going up, you can usually expect:

• Spiders, including black widows, spinning webs right around the fixture because it delivers their food
• Scorpions on nearby walls and along the ground below, picking off insects that drop
• Centipedes hunting the same patch
• Lizards working the wall around the light

In St. George, that second group is the real issue. Arizona bark scorpions climb stucco and block walls easily, and a well-lit wall full of insects gives them a reason to hang around your entry. Homeowners often keep treating for spiders and scorpions near the door without realizing the light a few feet away is feeding them.

What Reduces It

Change the color temperature. This one step does the most. Insects respond strongly to short wavelengths: ultraviolet, blue, and cool white. They respond much less to warm, long wavelengths.

Swap outdoor fixtures to warm white LEDs rated 2700K or lower, or to amber "bug light" bulbs. LEDs already beat older fluorescent and mercury vapor lights because they give off very little ultraviolet, but a cool white LED at 5000K still draws far more insects than a warm one.

Put the light somewhere other than the door. If you need a light for safety, mount it away from the entry and aim it back at the walkway. The insects collect there instead of at the door you walk through.

Use less light overall. Motion sensors beat dusk-to-dawn lighting. A swarm takes time to build, and a light that only turns on for a couple of minutes never gets one going.

Aim it down. Shielded fixtures that point at the ground light your path without broadcasting in every direction. Southern Utah is known for dark night skies, and downward lighting helps keep it that way.

Seal the gaps. Insects at the light still need a way in. Door sweeps, intact screens, and sealed openings keep an attraction from becoming an infestation.

Remember your windows. Uncovered windows at night act like lights too. Insects collect on the glass and slip in when the door opens.

What Does Not Work

Bug zappers. Studies show they mostly kill harmless and beneficial insects while doing little to the pests people care about, and they draw more insects to the yard than they kill.

Ultrasonic repellers. There is no solid evidence they repel insects.

Yellow bulbs that are still cool white inside. The tint of the glass matters less than the light actually produced. Check the listed color temperature, not the color of the bulb.

Practical Priority

If you only do one thing, change the bulbs over the doors you use most to warm white 2700K or amber. It is cheap, takes about ten minutes, and cuts down both the insects at the door and the spiders and scorpions that follow them.

If you are seeing more insects, spiders, or scorpions around your St. George home than you should, reach out to Butter Pest Control. Lighting is often part of the problem, and it is one of the easiest parts to fix.