The Lure of Lights to Flying Insects

The Lure of Lights to Flying Insects


The majority of insects captured in light traps inside a food warehouse or food plant are not food infesting pests. We can find stored product pests and filth flies but in most facilities, these are the smallest percentage of the total insect count. The majority of captures are light attracted insects which have made their way into the building through an open door.  They are often attracted to the building for the same reason that they end up in the trap, the lights.  They may breed in water, feed on vegetation or are predaceous on other insects and will not survive or reproduce in a food facility. Exterior light management and exclusion are the keys to reducing indoor problems with these insects.

What are some of the common invading insects?

Non-Biting Midges
Non-biting midges are medium sized, slender flies which are often mistaken for mosquitoes.  The males will have feathery antennae.  They can range in color but most are black or brown.  Unlike mosquitoes, they do not bite but are aquatic in nature.  Facilities near ponds or lakes will more commonly see midges of various types in their light traps.  These insects may be attracted to structures in large numbers particularly in the spring.

Leafhoppers are herbivores and feed on the juices of a variety of plants. They can be green, yellow, brown or a mixture of colors.  The body is wedged shaped and less than ¼ inch in size.  They may be found feeding on the underside of host plants outdoors.  It is a very common to find these insects in light traps.

Ground Beetles
The ground beetles comprise one of the largest groups of beetles in North America.  They are typically black in color with ridges on their wings.  One common species is bright green metallic and black in color.  They are active and night and will often fly to lights.  They are predaceous on insects and for this reason, considered beneficial in nature.

Thrips are extremely small insects, less than 1/20”, most are plant feeders.  They can range in color from white, to pale yellow to brown and are slender insects with fringes along their wings.  Although they are considered poor fliers, some will float on air currents and travel long distances.

Stink Bugs
There are a variety of stink bugs which may be found in insect light traps.  The green stink bug and the brown marmorated stink bug are two of the more common species.  The brown marmorated stink bug will intentionally enter structures in the fall for an overwintering harborage.  All stink bugs will have a triangular or shield like body shape and may be ½” or larger in size.  Most are pests of plants, feeding on plant juices with their sucking mouth parts.  They can be serious agricultural pests, causes damages in the millions of dollars to crops.  They are called stink bugs because of their ability to excrete offensive odors as a defense mechanism.

Night Flying Moths
There are several different species of night flying moths that may enter a building.  Most are agricultural or turf pests which leave the field and are attracted to the lights of structures.  They are drab in color with very little coloration on wings or wing patterns.  Examples of these moths include cutworms and army worms in the insect family, Noctuidae.

How are Flying Insects Controlled?

Although these insects are accidental invaders and will not reproduce indoors, they can contaminate products and packaging materials.  Reduction of their numbers indoors is important.  Reducing the attraction to the structure is the first step by managing exterior lighting.  The second step is reducing pest entry points through proper exclusion methods of keeping doors closed and other openings sealed or screened.

Insects use light in navigation and are attracted to lights for this reason.  The warmth of light may provide some secondary attraction.   Reducing the lights which are most attractive to insects like mercury vapor lighting in the 450 to 500 nm range is advised.  Use less attractive lighting like sodium vapor in the 575 to 600 nm range on buildings.  Use mercury vapor lights away from the building to pull them away from structures.  It is estimated that mercury vapor lighting is 112 times more attractive to insects than sodium vapor lighting which can provide major differences in the numbers of insects attracted to the building.  The mercury lights can be identified as having a stronger whitish blue light versus the sodium vapor lights which appear more yellow in tone or color.

LED lighting for exterior lights is becoming more popular.  The range of LED lights can vary considerably and before purchasing, the food plant should determine what range of light is emitted.  Avoid using LED lights in the same range as mercury vapor lighting ( 450-500 nm)  for fixtures which will mounted directly on the structure.

As mentioned previously, exclusion is another important element of managing these insects.  Food plant staff should be educated in the importance of keeping doors closed.  Timers and alarms can assist in insuring compliance.  Some facilities will also provide garage door type openers for forklift drivers to help increase compliance.  With these automatic opener devices, forklift drivers do not have to leave their forklifts to open and close doors which can facilitate the practice.