Spring Time Flies

From Langham Sask: What are the common springtime flies in our house? Every time this season, these flies are the first for a few weeks and then we do not see them until same time next year. Our house is clean, it is -5C outside, some are outside and some in our house. Where do they hid in the house for 10 months to appear every March?
Thank you for the reply.

My best guess would be that these most likely are cluster flies. These are not filth flies like house flies; their larvae feed on earthworms. These flies usually enter buildings or other shelter during the autumn, and then emerge from their hiding places with the return of warm weather in the spring. Click here for more detailed information.