Buffalo gnats, also known as black flies, are small, robust flies recognized by their distinctive humpbacked appearance. These insects are a common nuisance, as females often require a blood meal to produce eggs. This article addresses their global presence, preferred habitats, and seasonal activity patterns.
Global and Regional Presence
Black flies are found across nearly every continent, including North America, Europe, Asia, and Africa, except Antarctica and some isolated oceanic islands. Over 2,400 species are recorded globally. In North America, 255 species have been identified, with high prevalence in northern temperate and subarctic regions of Canada. Within the United States, they are common throughout most states, though their impact varies regionally. States like Minnesota, Wisconsin, and parts of the Northeast and upper Midwest experience significant black fly activity, as do areas like Arkansas’s White River region.
Preferred Habitats
The presence of flowing water is a primary factor determining where buffalo gnats thrive, as their larval and pupal stages develop exclusively in aquatic environments. These aquatic habitats vary widely, encompassing large rivers, icy mountain streams, trickling creeks, and even spillways of dams. The larvae attach themselves to submerged objects like rocks, vegetation, and leaves, using silk threads and hooks to anchor against the current.
Black flies prefer clean, non-polluted water with high levels of dissolved oxygen, a characteristic often found in swift currents. Larvae filter food particles from the flowing water. Adult black flies are most commonly encountered in close proximity to these water sources, though they can fly several miles. Human alterations to waterways, such as concrete dams, can even create additional suitable breeding sites for certain species.
Seasonal Activity
Buffalo gnats exhibit distinct seasonal emergence patterns, closely tied to water temperature and rainfall. In temperate regions, adults typically appear in late spring and early summer, a period often called “gnat season” due to intense biting activity. The life cycle from egg to adult is variable, depending on the specific black fly species and prevailing water temperatures. Eggs of many species hatch within 4-30 days, though some can remain dormant for several months. Larval development can range from a few weeks in warmer conditions to several months, especially if overwintering occurs. Outbreaks can also be influenced by heavy rainfall and cooler temperatures, leading to increased activity in certain spring periods.