Cluster Fly

Cluster Fly

Cluster Fly-Pollenia

Color- Black    Size-1cm-1.4cm   Legs- Six    Shape- Oval       Flying-Yes       Antenna-No

Region- Calgary, Alberta, Canada

These large, black flies are predominantly a house pest from late fall to early spring in the Calgary area. As the day cools off, the flies that clustered in the sun on the house wall, crawl in through crevasses and cracks, open windows and doors and under eaves.  Cluster flies begin as parasites within the bodies of earthworms thus they do not breed indoors.  They do however hibernate in their hiding place coming out of hibernation as the sun or indoor heat warms them.  Their crawling brings them into the house by way of electrical outlets, window pulley holes, and small openings around windows, moldings and base boards.  Because they hibernate in inaccessible places they are difficult to control. Preventing these flies is best in the summer and fall as much as possible.