Small flying insect in house

Question: Can you help identify and provide a recommendation on how to eliminate the small flying insects that we have had in the past month in one room of the house. They appear in the afternoon about 10-20 at a time. Fly to the window. They are easy to squish with your finger. I also have caught many in an envelope size sticky fly paper from my hardware store that I stick to a window.  My local pest control company has not been able to identify what they are.  They were not attracted  to a blue light mosquito trap or fruit fly traps.  After catching full  sticky traps of them for 2 weeks they stopped appearing altogether. They are about the size of a fruit fly.

responder: Howard Russell, Entomologist  Replied June 29, 2023, 12:38 PM EDT
response: Hello Gregory,  I can't be sure but my first thought is a sphaerocerid fly aka little dung fly (Diptera: Sphaeroceridae). Please send me a piece of that glue trap so I can confirm. Please wrap the trap in clear plastic wrap, then mail it in a box to  Plant and Pest Diagnostics 578 Wilson Rd.  East Lansing MI 48824-6469  Be sure to include a note with your contact information including your email address.  You can download one of our submittal forms here.  https://www.canr.msu.edu/pestid/uploads/files/Diagnostic%20Services%20submittal%20form%20012-001%20version%20July2019%20FILLABLE.pdf  We have a cart near the main entrance of the CIPS building where you can drop off your specimens if you like. Here is where we are located…https://www.canr.msu.edu/pestid/location  In nature, sphaerocerids are a very common and abundant group of flies that are usually associated with moist, decomposing organic matter. Spaerocerid larvae or maggots are known to develop in many habitats other than dung. These include carrion, fungi, compost, mammal nests, seaweed, conifer duff, cave debris and small deposits of dead vegetation. Very little is known of the life cycle of these flies, in fact, it is felt that most species of this family remain undescribed. Although found almost everywhere, sphaerocerids are of little agricultural or medical importance. A few species are commonly found in food processing plants and mushroom houses, and a number of species are reported to infest sewage systems. The best method of control would be to determine where the larvae are developing and remove the material. Look for decomposing organic material or fungi in moist areas in the basement or crawlspace, and forgotten bags of stored fruit and vegetables, and other such material.  Another possible cause for these flies occurring in homes in the fall, winter and early spring is that some species overwinter as adult flies under siding, in attics, wall voids, and other areas inside homes. In this case, it will be very difficult to rid the home of the flies until they leave or die on their own accord. If there is just a few flies, then any household aerosol insecticide, like Raid, will control them.  Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.  Regards,  Howard   *Tell us about your experience with our service by completing the brief (3 min.), anonymous MSU Plant & Pest Diagnostics Survey

responder: The Question Asker Replied June 30, 2023, 9:28 PM EDT
response: Thanks for your reply. I will get the sample in the mail so you will receive it next week. Have a good Independence Day. On Thu, Jun 29, 2023 at 12:38 PM Ask Extension <<personal data hidden>> wrote: