The type of insects that most people picture when hearing the word “flies” are common house flies and other similar looking winged insects that are frequently spotted within and around homes, such as fruit flies, drain flies, and blow flies. House flies and their similar looking relatives belong to the order Diptera, which includes nearly all known two-winged insect species including mosquitoes, gnats, and midges. The insect pests commonly referred to as flies can be divided into two groups known as indoor “filth flies” like house flies and fruit flies, and outdoor “biting flies” like stable flies and horse flies.

Indoor filth fly pests possess sponge-like mouthparts that allow specimens to soak up liquified foods, and they earn their name from their habit of breeding on organic waste materials, such as excrement, rotting food and decaying animal carcasses. Outdoor biting fly pests possess blade-like mouthparts that females use to pierce human skin in order to collect blood meals. Biting fly pests can be found throughout the US, but they are particularly problematic in the northeast where several species like greenhead and black fly pests attack humans in coastal and inland marsh areas.

Tabanus nigrovittatus, or the “greenhead fly” is the most well known biting fly pest in Massachusetts where large numbers emerge from marshland breeding sites during July and August. Males of this species use their sharp mouthparts solely for sucking juices from plants, but females must collect blood meals from humans or other mammalian species in order to lay viable eggs. The greenhead fly is a type of horsefly that resembles a large and partially green-colored house fly, and while they are known for inflicting numerous bites that cause significant pain and injury, they are not significant disease carriers. Since 2015, state authorities have been receiving reports about a new species of biting fly that has been attacking beachgoers along the Jersey Shore.

According to George Hamilton, the chair of entomology at Rutgers University, this new biting fly pest is probably a southern-dwelling horsefly species that has been migrating north due to the warming climate. Hamilton also states that since biting flies do not pose a disease threat to humans, public health authorities will not allocate the funds necessary to investigate the many reports concerning the mysterious biting fly pest. Some residents believe that the mystery fly species is Tabanus bovinus, or the “pale giant horsefly,” which is known to suck human blood, though they prefer the blood of other animals. Experts agree that this may be the species causing problems, as the mystery biting fly pest has been described many times as black and a bit larger than the greenhead fly, which describes T. bovinus.

Have you ever sustained bites from fly pests while in inland areas of Massachusetts?