Why are Flying Insects Attracted to Light?

You don’t have to be a pest control professional to know that insects are attracted to light. Just think of all those times you’ve seen moths and other insects frantically flying into or around the floruoscent light when it’s dark.

But have you considered that a greater understanding of this natural attraction to light can help to develop more effective insect light traps and a better fly control programme all together?

Research into this topic is of vital importance to businesses in the food industry, like food processing and food retail, helping to avoid outbreaks of fly-borne diseases like Salmonellosis.

The team of scientists at Rentokil’s Global Technical Centre has looked into understanding the physics of how light impacts the biological attraction of flies to a trap. This research has helped to  uncover LED technology as a far superior insect attractant than other conventional light sources.

When combined with a fly trap unit, LED technology offers the opportunity to capture and kill more flies than other conventional fly traps.

Do bugs like LED lights?

As homeowners, we have been convinced for a number of years now that LED lights are a smarter, more energy efficient way to light our homes. It seems this light source may also be highly attractive to insects.

What is it about the light from LEDs that is so attractive to flies?

The way light is emitted from LEDs is the reason they are particularly attractive to certain insects. LEDs produce UV-A as intense beams of light, which penetrate further into the surrounding space than light phosphor lamps, for example.

House flies are particularly attracted to UV-A as their eyes are sensitive to light at that wavelength.

Light attraction for flies

There is no single scientific explanation as to why flies are attracted to light. There are several theories which offer a possible explanation, as outlined below:

Using light for safety

For some insects, a bright light source may be seen as an emergency beacon.

When in doubt, these insects instinctively head towards light sources, which are generally positioned on higher ground than the hazardous environment they are currently in.

Light, for some insects, acts as a familiar safety signal, just as air bubbles leading the way to the water surface might help for other creatures.

Using light for navigation

Another popular theory for attraction to light, is that insects use it as a navigational aid.

An insect flying north for example, is able to judge its direction by keeping a natural source of light, such as the sun or moon, on its right. This method works well as long as the source of light remains both constant and at a distance.

If an insect encounters a round incandescent porch light, however, it becomes confused by its source. This explains the peculiar behaviour of a moth continuously encircling a light source – it instinctively wants to keep the light on a certain side of its body whilst navigating its route.

Phototaxis – an attraction to light

The difference between insects that are attracted to light and those which are not is a phenomenon known as phototaxis.

Certain insects, such as cockroaches or earthworms, have negative phototaxis, meaning they are repelled by an exposure to light.

Moths, flies and many other flying insects have positive phototaxis and are naturally attracted to it.

Debating science

There is some debate in the scientific community over why a positively phototactic insect, like a fly, will continue to hover around an artificial light source even when natural light becomes available.

Some believe that the insect is not attracted to the light itself, but the darkness surrounding it.

Others suggest the insect’s eyes, which often contain multiple lenses, struggle to adjust from light to dark, leaving the insect vulnerable to predators whilst night-blind. In this case, the insect may find it safer to remain in the light rather than fly away and become too blind to react to threats and obstacles.

Insect Light Traps and LED technology

Rentokil’s researches are able to prove the efficacy of insect light traps using LED technology through a standard Half-Life measure test. The Half-Life measure represents the time taken to eliminate 50% of flies released in a test chamber. The lower the Half-Life measure, the more effective the insect light trap.

An effective fly control programme must also consider the correct placement of a fly trap unit, given what we know about phototaxis.

This in-depth understanding of how light impacts the biological attraction of flies to a insect light trap demonstrates Rentokil’s expertise in pest control.

For more information on how we can help manage flies infestation in your business, please speak to our pest experts at 1300 881 911.