The American horse fly is one of the largest flies homeowners in Southern California will encounter, often reaching three-quarters of an inch to over an inch in length. It has a stout, robust body, large dark eyes that can appear iridescent green or striped, and smoky-gray to brown wings. Unlike the smaller house fly or blow fly, horse flies are strong, fast, and persistent flyers with an audible buzz, and only the females bite, requiring a blood meal to develop their eggs.
Horse flies are primarily an outdoor pest, and in the Los Angeles and Orange County area they tend to show up around properties near open fields, equestrian facilities, parks, and yards with standing water or dense vegetation, including areas bordering the San Fernando Valley and San Gabriel Valley foothills. Females are drawn to movement, warmth, and carbon dioxide, which is why they’re often encountered around patios, pools, and backyard gatherings during the warmer months, particularly near properties adjacent to horse boarding facilities or undeveloped land.
Unlike many household pests, the concern with horse flies is less about property damage and more about the immediate discomfort of their bite. Their mouthparts are built to cut and lap blood, which produces a sharp, painful bite in people and pets that can cause localized swelling and irritation. Because they can move between animals and people while feeding, they’re also considered by public health sources to be a potential mechanical carrier of certain organisms on their mouthparts, though the primary complaint from homeowners is almost always the bite itself.
Guarantee Pest Control has helped Los Angeles and Orange County families manage horse flies and other biting flies around their yards, pools, and outdoor living spaces since 1958. Our technicians will inspect your property for the standing water, vegetation, or conditions attracting horse fly activity and recommend an effective treatment plan to help you reclaim your outdoor space, with eco-friendly Guarantee Green options available. We offer free estimates, no-penalty cancellation, and a 3-month guarantee on most services. If horse flies are making it hard to enjoy your backyard, call 1-800-507-3787 or request a free estimate at /get-a-quote/.