‘Fruit Flies’ vs ‘Gnats’ vs ‘Drain Flies’ vs ‘Fleas’: What's the Difference?

By Amy Gilmore, updated on June 23, 2023

Are you wondering the difference between 'fruit flies' vs. 'gnats' vs. 'drain flies' vs. 'fleas?' If so, this guide will help.

Here is the short answer:

  • 'Fruit flies' are the most common flying bugs, and many times they are brought into homes on healthy fruit. They do not bite. 
  • 'Gnats' or fungus gnats are brown flies found around moist soil outside or potted plants indoors, and females suck blood like mosquitoes. 
  • 'Drain flies' or Psychodidae are distinctive non-biting black furry flying insects that are commonly found in drains. 
  • 'Fleas' are a type of wingless, parasitic bugs that jump onto mammals and feed on their blood. 

There is plenty more to learn about these flying pests. So, keep reading this guide to see learn the descriptions, definitions, and pronunciations of each.

What is the Difference Between 'Fruit Flies' vs. 'Gnats' vs. 'Drain Flies' vs. 'Fleas'

All four of these names refer to different pests.

Identifying 'Fruit Flies'

'Fruit flies' come in two varieties.

  • The smaller of the two has red eyes.
  • The larger variety has black eyes, and the smaller variety has black eyes.
  • 'Fruit flies' do not bite.

Identifying 'Gnats'

'Gnats' or fungus gnats are usually found outside.

  • They live in moist soil, and they are most frequently found outside.
  • 'Gnats' can bite you where you have exposed skin.

Identifying 'Drain Flies'

Psychodidae is the proper name for 'drain flies,' which are also known as bathroom flies.

  • These are the most distinctive flies and easiest to identify.
  • They are black with furry bodies and wings, and they look like tiny moths.
  • They are called 'drain flies,' but they are often found in the bathroom.

Identifying 'Fleas'

'Fleas' are the smallest of these insects.

  • The Ctenocephalides Felis or cat flea is the most common, but there are also dog fleas, rat fleas, and human fleas.
  • Each prefers a different host.
  • However, they will bite other hosts if you remove them from the host or if the host dies or doesn't provide enough nourishment for the parasitic bug.

When to Use 'Fruit Flies' vs. 'Gnats' vs. 'Drain Flies' vs. 'Fleas'

't Even after you know the meanings of these terms, it can be challenging to know when to use them.

So, here are a few tips.

  • Use 'fruit flies' to describe the flies you find in the kitchen flying around fruit or alcohol.

For example, you could say:

Sorry about these fruit flies. I brought home a bunch of fruit the other day, and they have been flying around ever since

  • Use 'gnats' to describe flies found in house plants or outdoor potted plants that bite.

For example, you might hear someone say:

These 'gnat' bites really itch. They are much worse than mosquito bites.

  • Use 'drain flies' to describe the small moth-like flies you find around drains in the bathroom and under sinks.

For example, you might say:

I don't know how to get rid of these 'drain flies.' They have been flying around the bathroom for the past week.

  • Use 'fleas' to describe the jumping, biting insects found on animals.

For example, I might say something like:

If you have pets, you have to use a flea control treatment to keep fleas at bay. 

Definition of 'Fruit Flies': What Does 'Fruit Flies' Mean?

According to the Merriam-Webster Dictionary, the definition of 'fruit flies' is:

  • Any fly that lays eggs on fruit and whose larvae feed on decaying fruits and vegetables

Definition of 'Gnats': What Does 'Gnats' Mean?

The same dictionary defines 'gnats' as:

  • Flying, biting insects

Definition of 'Drain Flies': What Does 'Drain Flies' Mean?

There is no definition for 'drain flies' in the Merriam-Webster Dictionary.

However, there is a definition for the proper name, which is Psychodidae:

  • A family of furry dipteran flies that do not bite but are present in unsanitary bathroom conditions

Definition of 'Fleas': What Does 'Fleas' Mean?

The definition of 'fleas' is:

  • A wingless blood-sucking insect that leaps onto a host and sucks its blood

Pronunciation: How to Pronounce 'Fruit Flies' vs. 'Gnats' vs. 'Drain Flies' vs. 'Fleas'

Now that you understand the definitions and usages of these names for common insects, let's look at the pronunciations. Knowing how to pronounce these terms will help you use them more confidently.

  • Use this phonetic spelling to pronounce 'fruit flies':

früt flīz

  • Use this phonetic spelling to pronounce 'gnats':


  • Here is the phonetic spelling of 'drain flies':

drān flīz

  • This is the phonetic spelling of 'fleas':


Sample Sentences Using 'Fruit Flies' vs. 'Gnats' vs. 'Drain Flies' vs. 'Fleas'

Finally, before you go, take a look at these sample sentences using 'fruit flies' vs. 'gnats' vs. 'dain flies' vs. 'fleas.'

Fruit Flies

  • Flypaper is a good way to control fruit flies.
  • If you buy a lot of fresh fruits and vegetables, you will likely have fruit flies in your home.
  • You sometimes see fruit flies in the produce section of the grocery store.


  • I have itchy gnat bites all over my legs.
  • I love being outside, but these gnats are driving me crazy.
  • If you have a lot of potted plants indoors, you are more likely to get gnats in your home.

Drain Flies

  • Cleaning that apartment was horrible. There were drain flies all over the bathroom.
  • Drain flies are not common in most homes, but they are terrible to get rid of if they are in your house.
  • The drain flies look like baby moths, but they do not damage clothing.


  • Fleas plague yards in the South, especially during the summer months.
  • Homeowners in most parts of the country get a much-needed break from fighting fleas during winter.
  • There are effective lawn treatments that help to fight flea infestations.

The Last Word on the Difference Between 'Fruit Flies' vs. 'Gnats' vs. 'Drain Flies' vs. 'Fleas'

We covered a lot of information. So, let's do a quick recap: 

  • 'Fruit flies' lay eggs on produce, and their larvae feed on the decaying fruit. They come in different sizes, but they do not bite. 
  • 'Gnats' are typically found outside in moist soil, and the females bite to suck blood they need to reproduce like mosquitoes. 
  • 'Drain gnats' are moth-like bugs found in bathroom drains with unsanitary conditions, but they do not bite.
  • 'Fleas' do not fly. They are leaping insects that live on a host animal, like a dog or cat, but they can also bite humans. 

Remembering the difference between these 'fruit flies' vs. 'gnats' vs. 'drain flies' vs. 'fleas' can be challenging, so if you get mixed up in the future, you can always come back to review this lesson.

In our confusing words section, you can also learn the difference between other commonly misused English terms. Each post contains definitions, pronunciations, and usage examples. So, they are an excellent way to expand your vocabulary while learning essential grammar rules.

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Written By:
Amy Gilmore
Amy Gilmore is one of the lead freelance writers for WritingTips.org. She has been a professional writer and editor for the past eight years. She developed a love of language arts and literature in school and decided to become a professional freelance writer after a demanding career in real estate. Amy is constantly learning to become a better writer and loves sharing tips with other writers who want to do the same.

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