Tiny black bugs

Asked March 23, 2015, 6:09 PM EDT


Around 5 months ago I had an infestation of tiny black bugs in my kitchen window. They did fly, although they mostly ran. Every morning I would find around 35 bugs in the kitchen window and floor, most of them dead. Sometimes I would see them flying in my bedroom or living room, but just a couple of them. I cleared my trash every day and they didn’t go. I even found some inside my fridge. A pest control company came, and bombed and sprayed my place. Their theory is that they were fleas (nor sure about it) After that, I still saw a couple of them and decided to throw away some organic soil I had for my plants. After that, they were gone, but also the winter came.

A few weeks ago I think I saw a similar little black bug flying a couple of times, once in my bedroom, once in my living room. But then nothing happened, so I thought those were probably different.

Yesterday I saw one of the bugs AGAIN in the kitchen window sill. It is a bit larger than the ones I saw before, but I think it is the same bug. It was dead. This morning I was another two! One is minuscule, the other one a but bigger, but smaller than the one I saw first. I left my kitchen window open for 2 days for the first time in months, as the winter here (Cambridge, MA) is extremely cold. I’m very concerned cause I don’t know if maybe there is a nest outside my window (how did they survive the winter?!) or if there is something hidden in my place. I don’t think they are fleas, as they do fly, and I don’t have any animals, nor bites. Please help me! I’m attaching a picture of the bigger one I found this time.

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Nantucket County Massachusetts urban integrated pest management

5 Responses

Good to have nice images! You are dealing with phorid flies. These are commonly called humpbacked flies or scuttle flies because they have an arched back and tend to scoot rapidly back and forth. The larvae of these flies feed on decaying organic matter, especially material that has animal fats in it. We get infestations of these around restaurants where the grease trap isn’t being cleaned regularly or they are letting moist fats and oils accumulate under or around the kitchen. The flies will also breed in drains where food material and fats are entering. The best way to control this fly is through thorough cleaning and diligent sanitation.

In home situations, be sure to regularly clean your garbage cans (using plastic bags helps, but any goo that escapes into the can will serve as food for the maggots of this fly), be sure that your outside garbage is being regularly disposed of and the cans or dumpsters are being cleaned periodically. If possible, pull out the stove and check to ensure that no fats, oils and food waste has accumulated under or around it. Most refrigerators also have drip pans located in the bottoms. These should be checked and cleaned as they can accumulate dust and debris that is kept moist by the condensation. If you have floor drains (especially in the basement), pour a bucket of water through these on a monthly basis in order to eliminate any debris that may be accumulating in the traps. This can also serve as food for these flies. Be sure to check the outside of your home or building to see if there is any place that wet, decaying plant material is allowed to set! This fly can complete its life cycle in 15 to 20 days in warm weather. Homeowner compost piles that are kept too wet are a common problem!

There are several factsheets on this fly. I have attached a link below, but if it doesn’t work, just Google “phorid flies” and scroll down until you see the Colorado State or Clemson links.


Avatar_placeholder_01 David S.
Replied March 24, 2015, 12:06 PM EDT

Hello David,

Thanks a lot for your thorough answer. I will try to keep my trash out everyday. However, I don’t have animal fat in my kitchen. I barely cook meat here.

I am concerned because they disappeared for many months and then now, when it is getting warmer, they might be back. Is there any explanation for that? Is it possible they are coming in from a pipeline close to my window, as it was only when I left it open for a few days that I found them?

Does the fact that I found 3 dead ones, one big and 2 smaller ones, indicates they might have laid eggs in my kitchen?

Again, thanks a lot.

Anonymous Guest

Replied March 24, 2015, 12:38 PM EDT

Yes, with them being absent during the winter months, this would indicate that they are more likely breeding outside, but nearby. The larger one was likely female and the smaller ones were males. There is a considerable size difference between the sexes. If they were dead, this would also indicate that your dwelling is likely not a good place for them (too dry)…which would be a good thing! LOL!

I’m a little annoyed that your pest control professional didn’t know what these were! Area sprays and fogging is of little use against these flies as neither treatment will get to where the larvae are feeding. The flies are fairly common and we are getting increasing reports of them, especially in food handling facilities and hospitals! The last hospital I worked with that had an issue with these flies, the cause was traced to a broken sewer pipe that ran out of the basement! This was dumping “gunk” into the soil and the larvae were breeding in that! Not an easy fix, but when the pipe was fixed, no more flies!

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