Maine is known for its natural beauty, but also for its black fly population. These small, biting insects are a frequent topic of conversation, as their presence can significantly impact outdoor activities. Many seek information on when to expect their peak activity. Understanding these insects and their seasonal patterns helps people navigate the outdoors more comfortably.
Understanding Maine’s Black Flies
Black flies are small, dark insects, typically measuring less than one-eighth of an inch. In Maine, approximately 40 to 50 species exist, though only a small number actively bite humans. Female black flies require a blood meal to nourish their developing eggs, while males feed on plant nectar.
Their life cycle depends on clean, flowing water. Eggs are laid in fast-moving creeks and rivers, where larvae hatch and attach to submerged objects. Larvae filter organic matter from the current for food, then pupate underwater. Adults emerge from the water, unfolding their wings and flying off. Maine’s extensive network of clean, running waterways provides an ideal habitat, contributing to their widespread presence.
Peak Black Fly Season in Maine
Historically, Maine’s black fly season ran from late May through early June, often coinciding with the period between Mother’s Day and Father’s Day. However, due to improvements in water quality over recent decades, the season has notably extended. Black flies can now be present from May into October, with different species emerging throughout this period.
The timing and intensity of black fly activity are influenced by environmental conditions. They generally become active when air temperatures rise above 50 degrees Fahrenheit. Black flies tend to be more active on humid, cloudy days and just before storms, while strong breezes and bright sun can help keep them at bay. Their daily activity often peaks in the late morning and early evening.
Regional variations also affect the season’s progression across Maine. The black fly season typically advances from south to north and from coastal plains to inland areas and higher elevations. Some species, such as Simulium penobscotensis in the Penobscot River valley, can persist and produce multiple generations, remaining active until the first hard frost. This means that while some areas may see a reduction in black fly numbers by mid-July, other locations might experience continued activity through the late summer and fall.
Preparing for Black Fly Season
To minimize discomfort during black fly season, several preventative measures can be employed. Using insect repellents containing DEET or picaridin is effective. Natural repellents with essential oils like peppermint, rosemary, cedarwood, or geranium may also be helpful, though these may require more frequent application.
Wearing appropriate clothing provides a physical barrier against bites. Long-sleeved shirts and long pants are recommended. Choosing light-colored garments can be beneficial, as black flies are attracted to darker hues. Head nets are valuable, especially since black flies are drawn to the carbon dioxide in exhaled breath and tend to swarm around the head.
Timing outdoor activities can reduce exposure. Since black flies are less active at night and when strong breezes are present, choosing to be outdoors during these times or in open, windy areas can provide some relief. Avoiding densely wooded areas or locations directly adjacent to running water, where they breed, can also help reduce encounters.