When gnats attack

Original artwork by Tom Bone

BLUEFIELD — Call them gnats, or call them fruit flies, or flying spawns of satan sent from the fiery depths of hell to drive humankind mad. Summer’s teeny-weeny demons have now come to a kitchen or office near you.

Summer is here and it has brought its insect population, in force. According to Virginia Tech’s Urban Pest Manager Professor, Dr. Dini Miller, there are 137 species of dark-winged fungus gnats and fungus gnats who belong to one category of gnats on the east coast. However, between the United States and Canada alone, there are 714 species of gnats.

The kind of gnat that most people have in their homes are the dark-winged fungus gnat. They are technically a type of fly but they cannot bite and carry no disease, they are just an annoyance.

“Their major food source when they are larvae is soil,” Dr. Miller said. “They go through stages while living in soil: the egg, the larvae, which is the worm-like individual and then the four-eye emergence later. The adult flies will lay their eggs in moist soil and then the larvae hatch and eat soil and then the adults with emerge.”

Unfortunately, the gnats and fruit flies that plague the precious, air-conditioned indoors of the summertime, come from another summertime staple, potted plants and fresh fruit.

While they may be commonly confused, gnats and fruit flies are different insects. Gnats are generally laid and emerge from the soil. Fruit flies breed in fermenting fruit. So, if there is something as simple as a bruised apple in the kitchen, the fruit fly can breed there.

“Fruit flies are usually outside and associated with rotting fruit,” Dr. Miller said. “When they get indoors they are usually attracted to fermenting fruit. Say you go to the store and buy some nectarines and some of them are bruised and they sit in your house, their flesh will start to ferment and that attracts the fruit flies. They are attracted to vinegar fermentation.”

“What we see a lot this time of year, people put potted plants outside then bring them in. If the plants have been watered by natural rainfall and when they dry out, the gnats will emerge seeking moisture,” Dr. Miller said. “An easy way to solve it is to put the plant back outside. It really won’t stop the emergence of the gnats, but they will be outside.”

While fruit flies are attracted to the fresh summer fruit indoors, most gnats are attracted to soil.

Dr. Miller said one way to keep the gnats in the soil of potted plants is regular watering, but this is a catch-22 of sorts: keeping potted plants watered creates an optimal habitat for gnats. They may stay in the soil, but they will lay more eggs, creating more gnats next year.

Nature will, as nature does, as they say, so the cycle will continue with, or without human interference. In that same grain, what is the purpose of gnats in the ecosystem? After all, everything has its place. Well, it turns out that gnats purpose in the world is to be food for carnivorous insects.

“They do not do anything beneficial for the ecosystem indoors. They are food for other insects outdoors,” Dr. Miller said. “They are quite tiny and even a mouse would have to eat a couple hundred of them for a full meal. More carnivorous insects would feed off of them. We have a lot of carnivorous true bugs, things like the Wheel Bug, the Cone Nose bug and what they do is feed on other insects.”

Gnats purpose in their own tiny minds is to seek moisture and mate. So, according to Dr. Miller, one of the reasons gnats hover around human faces creating an annoyance is because of the moisture of our eyes.

“They are desperate for moisture even as adults and that is what attracts them to food,” Dr. Miller said. “Anything that is moist is going to be more attractive to them.”

If she had to guess, Dr. Miller said the lifespan of an adult gnat would be around two days.

“Their lifetime, under optimal situations, adults emerge in about three days, one of the issues we have with most insects that live indoors and are not meant to, the lack of humidity from our air conditioning systems kills them off pretty quickly,” Dr. Miller said.

Insects are just a part of life, especially in the summertime. Thankfully, two of the most common species that invade homes, gnats and fruit flies, are not harmful to humans physically. They do not feed off of blood. However, there is no study available that proves they do not enjoy annoying human-kind all summer long. Who knows what might be going on inside those tiny minds?

— Contact Emily Rice at erice@bdtonline.com and follow her on Twitter @BDTrice