Fruit fly vs Gnat: Know your common household pests

Congrats, your fruit fly trap is perfect and all all set, except that the culprits in question aren’t fruit flies but gnats! Same to you over there! You’re wasting your time repotting the houseplants and monitoring water levels every now and then, your problems arent fungus gnats but pesky little fruit flies!

These two creatures aren’t the same thing, aren’t attracted indoors by the same thing and matter of fact, don’t even look the same when inspected closely. This therefore means, that each one of them would require different treatments and solutions (although fruit fly traps can sometimes work for certain types of gnats) for their indoors extermination.

In this article, we’ll try our best to portray the differences between fruit flies and gnats so that you may be able to tell apart one species from the other and progress swiftly with appropriate treatments for eradication.

Fruit fly vs Gnat

s/n Entries Fruit fly Gnat
1 Size 2 to 4 mm 1 to 7 mm
2 Body shape Similar to common housefly. Mostly similar to a mosquito. Some however, can have fat short abdomens which sharply contrast with the slender thorax and small head (upper body).
3 Head features and size, eye size and color Relatively big heads. Prominent eyes with red or black pigment. Usually short antennas. Usually small heads. Inconspicuous (tiny) eyes with black pigment. Short to long antennas relative to body size.
4 Thorax (neck) color Typically pale yellow to reddish brown and sometimes black at the top. Some species can have white stripes running across the top of head and thorax. Typically yellow, red, brown and some times black or gray. Some species can have humped thorax.
5 Abdomen color Can be: a) reddish brown to black at the top with cream to pale yellow underside. b) cream to reddish brown to black all over c) cream to reddish brown with thin to thick dark spots or transverse rings spread across or all over the abdomen. Or, the other way round. Can be: cream to pale yellow to reddish brown to black. Dark spots can also be present.
6 Wings Typically a single translucent pair with or without spots or patterned bands. Typically a single pair of translucent or dark wings with or without spots or patterned bands. Females may or may not have wings.
7 Most species feed on Anything with a moist film of rotting or fermenting stuff especially fruits and vegetables. But some species are also known to infest ripening soft summer fruits such as berries, apricots, peaches and grapes. Plants leaves and roots, fungi present in soil, rotting and decaying organic matter in soil and drains, blood, and other insects alike.
8 Preferred areas of indoors infestation Kitchen: in sink, drain and around fruit baskets. Trash cans. Moist areas i.e plant potters, clogged gutters, damp woods, damp drywalls or the garden.
9 Bite Non-biting. Only a nuisance. Can be both biting and non-biting.
10 Potential harm to humans Not by themselves, but can transfer disease causing bacteria. Some gnats species like the black fly can spread diseases.


How to tell fruit flies and gnats apart

Telling apart fruit flies from gnats is an easy endeavor even for the average guy at home. We’ll be using two main characteristics for the task. First is external morphology of both flies and second is the attractants for both insect groups. So let’s quickly get started before it gets boring. I know you’re probably exhausted from assimilating the monstrous table from above. That’s why i’ll try as much as possible to keep the explanations short, simple and easy to follow.

1) External morphology

Head region: Most fruit flies have relatively big heads with prominent eyes in comparison to gnats who have tiny heads with nearly inconspicuous eyes. The  color of the eyes in fruit flies is mostly brick red but can also adopt a brown to black coloration. This color is due to two pigment in the eyes called Xanthommatin and Drosopterins which are both brown and red respectively. Gnats on the other hand have eyes that are mostly dark brown to black in coloration. Another thing about fruit flies is that most of them have very short antennas at the top of their heads whereas gnats can have medium to long antennas on top of their heads relative to their body sizes.

Thorax and abdomen (Body region): Almost all fruit flies currently on the scientific index have thorax equal to or a bit fatter and elongated than those of gnats. The thorax region which is kind of similar to necks in humans is usually pale yellow to reddish brown or sometimes black. Or, It could have all these colors at the top with a cream to reddish brown coloration at the underside. Some species of fruit flies for example the Drosophila Suzukii can have can even or odd number of white stripes running across the top of head and thorax. In gnats, the thorax can be yellowish to reddish brownish or even black or gray (mostly). Some species of gnats for example the popular fungus gnats, can have humped thorax.

Fruit flies have abdomens the shape of strawberries. The colors often match that of the thorax in most cases but can sometimes be different in which case the abdomen can be reddish brown to black at the top with cream to pale yellow underside or cream to reddish brown with thin to thick dark spots or transverse rings spread across or all over. Or, the other way round. For gnats, the abdominal region is slender and elongated and just like in fruit flies, it usually picks up the same coloration as the thorax but some species of gnats can have cream to yellow underside with or without spots or transverse rings spread across or all over.

Wings: Fruit flies have a single translucent pair of wings with or without spots or patterned bands. Gnats on the other hand have a single pair of translucent or dark wings with or without spots or patterned bands. Some female gnats are actually wingless.

Legs: Fruit flies overall, have shorter legs compared to gnats.

What are both fruit flies and gnats mostly attracted to while indoors?

Both fruit flies and gnats are free living wild animals. When they aren’t in the wild lapping up nutriments from their respective sources, they are somewhere within the metropolis making residence out people’s apartments in specific areas that sharply contrast one another. Here’s what lures both fruit flies and gnats into the house and where they are mostly found while indoors.

Fruit fly attractants: Most fruit flies found at home usually infest areas such as kitchen sink, drains, trash cans, refrigerators, food store and fruit bowls on counter tops where moist film of fermenting or rotting items are likely present. Fruit flies are easily lured into the house by the scent of fermenting fruits and vegetables which they can quickly detect from distances greater than one kilometres. While in the house, fruit flies breed as quickly as possible within these medium in order to give birth to as much as 50 babies in less than a week after copulation. In the wild, fruit flies reside and thrive in rotten plant materials for example, rotten mushrooms and fruits.

While it has been established that fruit flies prefer to live within and mostly consume rotten fruits and vegetables, not all species within the fruit fly group actually do so. The Drosophila suzukii (also known as the spotted wing drosophila) and Scaptomyza flava are the greatest examples of the exceptions. The former infests thin-skinned fruits such as berries and cherries during their ripening stages whereas the latter is the only known herbivore member of the fruit fly family; depending on plant leaves particularly those of the mustard plants for sustenance. Drosophila suzukii is regarded as a serious agricultural pests in the regions where it’s commonly found such as the Americas, Europe and southeast Asia. Likewise, Scaptomyza flava is also a well recognised pest in Europe and New Zealand.

Gnat attractants: Most gnats found at home are usually the fungivores that infest potted plants located inside, outside or in the garden. Blood sucking gnats are also popular species indoors and are known to derive sustenance from sucking blood of humans and other mammals. Fungivore gnats are easily lured to moist areas (or wet soils of your pots) in their huge colonies called clouds from wherever they are if close by. They often arrive at dusk. The adults of herbivorous gnats most often pose little threats compared to the larva stages of their eggs. They are mostly a source of nuisance in huge groups. The former in larger numbers (which is usually the case since females can lay eggs up to 300 per breeding season) can easily consume plant roots and leaves and causing damage to potted house plants. Even though they may do so, these gnats mostly feed on fungus, algae and decaying organic matters first.

The most common type of indoor fruit flies 

  1. Drosophila Melanogaster: The most commonly encountered fruit fly indoors is a species called Drosophila Melanogaster. This fruit fly is also referred to as the common fruit fly or the Vinegar fly, deriving this name from the popular remedy of vinegar with dish soap in a jar used for eliminating them. The common fruit fly has huge brick red eyes with yellow to reddish brown body. It’s total body length is only a matter of millimetres, usually around the 2 to 3 mm mark and often nothing more than that. Females are larger than males and have the fewer numbers of darker transverse rings across their abdomen. The tip of the abdomen in males usually has the thickest transverse ring.
  2. Drosophila suzukii: One notorious species of fruit flies found in Europe, Americas and southeast Asia is the Drosophila suzukkii also known as the spotted wing drosophila. This species is different from most members of the fruit fly family in that it feeds primarily on soft fresh and ripening fruits rather than rotten or fermenting materials. The females burrow into the ripening fruits with their serrated ovipositors and deposit clutch of 1 to 3 eggs per insertion, up to 50 in a season. The larvae develops inside the fruit while feeding and deriving nutriments, then pupate and turn into adults. Because of this habit of burrowing deep into ripening fruits and deposition eggs, D. suzukii is regarded as an economical pests since they end up damaging huge numbers fruits from commercial farms.
  3. Zaprionus Indianus Gupta: This species is a recognized agricultural pest in the new world primarily attacking and destroying fig fruits. Their primary range includes Africa and southeast Asia. They are easily recognized by having even or odd number of stripes running across the top of their heads and thorax.

The most common type of indoor gnats

  1. Fungus gnat: Fungus gnat is one of the most commonly found gnats at home. If you’re currently dealing with a gnat infestation, huge chances are, that you have yourself a fungus gnat infestation. These non-biting pests are typically black, small and mosquito like in nature and are commonly found within the vicinity of houseplants. They have hump thorax. Their larvae are regarded as the bigger pests since they are deposited into the soils of potted plants or garden plants and usually end up feeding on the roots when competition become severe, i.e when eggs are laid in huge numbers. Adult fungus gnats are weak fliers and can mostly be seen hovering around plants but can also disperse shot distances to reach around window frames and lamps. They are particularly fond of light and color yellow and that can be used as a means of capturing them.
  2. Black fly: Black fly are species of gnats that bite. They are blood sucking flies that may be gray, tan or even greenish in appearance. They usually have a distinctive hump at the back of their head. Bites from black flies can cause sever allergic reactions in some individuals and its usually very painful and itchy. Black flies feed mainly on the blood of humans and other mammals.

How to get rid of fruit flies and fungus gnats?

If you have successfully identified a fruit fly infestation in your home, you can use the detailed guide below to send them packing out of the house.

  1. What is the fastest way to get rid of fruit flies?

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