Fireflies can help control garden pests

Garrard Coffey
Agriculture and Natural Resources

Fireflies evoke memories of a childhood chase. You’d catch one in your hand and wait to see the flickering light and then moments later, release it unharmed and watch it fly away.

This summertime favorite does more than generate entertaining childhood memories. They also help control some pests in your garden. On summer nights, glow worms (luminescent firefly larvae) often emerge from their underground homes to forage for food.

A typical menu includes slugs, snails and caterpillars including cutworms. The larvae feed much like a spider by injecting a paralyzing toxin into their prey; then, injecting digestive juices to dissolve the prey and allow it to be more easily consumed. The adults probably feed on plant nectar to sustain their energy requirements.

There are several theories about why fireflies glow. One is that the flashing light is a homing beacon for the opposite sex. The male flies around flashing the signal to attract a female’s attention. A female on the ground or on low-growing foliage will signal back when a male visits her vicinity. To avoid confusion, each firefly species has its own specific signal to attract a mate.

Another theory is that firefly larvae use their luminescence to warn a potential predator that they taste bad. Larvae contain defensive chemicals in their bodies. When disturbed, larvae also increase their glow’s intensity and frequency.

Typical nighttime habitats for adults and larvae take place in rotting wood or other forest litter, or on the edges of water sources such as streams, ponds, marshes and ditches.

The highest species diversity is in tropical Asia and Central and South America. Incidentally, some Asian species have tracheal gills that enable them to live under water where they feed on aquatic snails.

To attract fireflies to your property, reduce or eliminate lawn chemicals. Add low, overhanging trees, tall grass and similar vegetation to give adult fireflies a cool place to rest during the day. Reduce extra lighting on your property because this light interferes with fireflies’ luminous signals, making it harder for them to locate mates in the area. Fireflies also determine the time of night they’ll flash by the intensity of ambient light. This is why you don’t see many fireflies flashing on clear nights with a full moon.

For more information, contact your Whitley County Cooperative Extension Service at 549-1430; e-mail DL_CES_WHITLEY@EMAIL.UKY.EDU; or visit the office located at 4275 N. Highway 25W in Goldbug.