cluster fly against a white background - Keep cluster flies away from your home with Kona Coast Pest Control in Kailua Kona

Cluster Fly

Actual Size: 8 mm

Characteristics: Dark gray in color; non-metallic.

Legs: 6

Wings: Yes

Antennae: Yes

Habitat: Attracted to ripe fruit and flowers; seek shelter inside buildings during winter.


  • Have a similar appearance to house flies, though they are noticeably larger.
  • Cluster flies may emit a distinctive, sickly-sweet odor when disturbed or crushed.
  • Seek refuge inside homes and other structures during the winter. 
  • Unlike blowflies, cluster flies do not exhibit an interest in human foods.
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Cluster Flies in Kailua Kona

Cluster flies, belonging to the blowfly family, can be found across the United States, with the exception of states bordering Mexico. As autumn approaches, these insects seek hibernation and gather in concealed locations like wall cavities, attics, and false ceilings. During their period of inactivity, they inadvertently find their way into living spaces when they become active again in spring. While their presence may pose a nuisance, it’s worth noting that cluster flies, in comparison to many other fly species, are not attracted to human foods, distinguishing them as relatively quiet and harmless house guests.

Cluster Fly Habitat

Typically residing outdoors, cluster flies are commonly found around flowers and ripe fruits. As cooler weather approaches, they seek shelter indoors, often gathering in clusters in hidden corners, underneath clothing in closets, behind curtains, in wall voids, and behind pictures and furniture. As spring days become warmer, their activity increases, and the flies may emerge from hibernation inside homes rather than outside. Once indoors, the cluster flies crawl slowly over walls and may fall into your food.

Cluster Fly Behaviors, Threats, or Dangers

Unlike regular blowflies, cluster flies are not considered a health risk because they do not display an attraction to human foods. Nevertheless, their presence can be frustrating, given their inclination to travel in large swarms numbering in the thousands. In the fall, these adult flies gather near windows in buildings and homes, generating a noisy buzz as they look for shelter during the winter months. Swatting them can result in greasy spots, and their accumulated excrement during hibernation may emit a noticeable odor and potentially stain fabrics and walls.

If you are dealing with a cluster fly problem on your property, contact your local fly exterminators.