Black flies are a common presence in Upper Michigan’s wooded and watery regions. These small, biting insects cause discomfort, detracting from outdoor experiences. Understanding their seasonal patterns is important for enjoying the area.
Understanding the Black Fly Season in Upper Michigan
Black flies typically emerge in Upper Michigan starting in late April or mid-May, with peak activity often occurring from mid-May through mid-July. While the most intense period lasts several weeks, different species can prolong their presence into August and early September. They are especially prevalent in the western Upper Peninsula and along the Lake Superior shoreline.
The life cycle and activity of black flies are closely tied to environmental factors, especially the availability of clean, flowing water. Their larvae develop in well-oxygenated rivers and streams, where females lay their eggs on submerged objects. Water temperature and the runoff from snowmelt significantly influence when eggs hatch and how quickly larvae mature into adults. Cooler, wetter spring conditions can sometimes delay their initial emergence or extend their season slightly, while hot and dry weather may lead to a quicker decline in their populations.
Black flies are typically most active during daylight hours, often exhibiting heightened activity around dawn and dusk on calm days. They are drawn to humans and other warm-blooded animals primarily by the carbon dioxide exhaled, as well as perspiration, certain fragrances, and dark, moving objects. While the female black fly requires a blood meal for egg development, male black flies feed on nectar and do not bite.
Tips for Dealing with Black Flies
To minimize encounters with black flies during their active season, strategic clothing choices provide a physical barrier. Wearing light-colored clothing is advisable, as black flies are attracted to darker hues. Long-sleeved shirts and long pants made of tightly woven fabric can prevent bites, as these insects generally cannot bite through clothing. Tucking pant legs into socks or boots and shirts into pants can further deter them from crawling onto exposed skin.
For comprehensive protection, especially in areas with high black fly populations, a head net is particularly effective at keeping them away from the face, ears, and neck. Insect repellents offer a layer of defense. Repellents containing DEET or picaridin are often recommended, with picaridin noted by some sources as potentially more effective against biting flies compared to DEET. For clothing and gear, products containing permethrin can be applied to provide additional protection.
Avoiding areas known for intense black fly activity, particularly near flowing water where they breed, and limiting outdoor exposure during peak biting times like dawn and dusk can also reduce the likelihood of bites. If a bite occurs, prompt treatment can help alleviate discomfort. Washing the affected area with mild soap and water, applying a cold compress, and using over-the-counter anti-itch creams such as hydrocortisone or calamine lotion can help manage symptoms like itching and swelling.