What kind of insect is infesting my house? - Ask Extension
My home is being infested by a tiny flying black insect. I thought they were fungus gnats, but after seeing pictures on the internet I'm not so sure.Â...
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What kind of insect is infesting my house? #802289
Asked July 21, 2022, 9:25 AM EDT
My home is being infested by a tiny flying black insect. I thought they were fungus gnats, but after seeing pictures on the internet I'm not so sure. The insects are lazy flyers, and leave what appears to be blood when squished. Can you help?
Thanks in advance - much appreciated!
-Dave
Bucks County Pennsylvania
Expert Response
Forgot to mention - these are very tiny, 2-4mm
-Dave
The fly in the photos is a dark-eyed vinegar fly (Drosophila repleta).
Dark-eyed vinegar flies are about twice the size of red-eyed vinegar flies, which people often associate with bananas and other fruit. And unlike red-eyed vinegar flies, dark-eyed vinegar flies breed in wet organic matter rather than rotting fruit.
In private homes, this can include things like rotting potatoes (which has happened to me) and perhaps the bacterial build up in drains. In commercial buildings, other potential food sources include food caught under a cracked floor tile in a restaurant, coffee grounds around a floor drain in a coffee shop, or anything similar. Basically, if it's wet and organic it may support the larvae.
Finding and removing the wet organic matter the flies are breeding in is the best way to control them. However, if you can't find the larval food source, you can trap the adult flies to reduce, if not eventually eliminate, the population. Because they breed in wet organic matter instead of fruit, dark-eyed vinegar flies aren't attracted to and controlled by apple cider vinegar traps like red-eyed vinegar flies are. This can cause homeowners a lot of consternation when they wonder why their vinegar traps don't work. However, dark-eyed vinegar flies are attracted to red wine, so using the same type of inverted cone trap and replacing vinegar with red wine can get the control homeowners are looking for. The type of red wine doesn't matter, so if you don't like wine, a $5 bottom shelf bottle is just fine, but if you like wine, you could treat yourself to a nicer bottle and sacrifice a bit for the trap.
Dark-eyed vinegar flies are about twice the size of red-eyed vinegar flies, which people often associate with bananas and other fruit. And unlike red-eyed vinegar flies, dark-eyed vinegar flies breed in wet organic matter rather than rotting fruit.
In private homes, this can include things like rotting potatoes (which has happened to me) and perhaps the bacterial build up in drains. In commercial buildings, other potential food sources include food caught under a cracked floor tile in a restaurant, coffee grounds around a floor drain in a coffee shop, or anything similar. Basically, if it's wet and organic it may support the larvae.
Finding and removing the wet organic matter the flies are breeding in is the best way to control them. However, if you can't find the larval food source, you can trap the adult flies to reduce, if not eventually eliminate, the population. Because they breed in wet organic matter instead of fruit, dark-eyed vinegar flies aren't attracted to and controlled by apple cider vinegar traps like red-eyed vinegar flies are. This can cause homeowners a lot of consternation when they wonder why their vinegar traps don't work. However, dark-eyed vinegar flies are attracted to red wine, so using the same type of inverted cone trap and replacing vinegar with red wine can get the control homeowners are looking for. The type of red wine doesn't matter, so if you don't like wine, a $5 bottom shelf bottle is just fine, but if you like wine, you could treat yourself to a nicer bottle and sacrifice a bit for the trap.
