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March Brown Mayfly (Maccaffertium vicarium)


Detailing the physical features, habits, territorial reach and other identifying qualities of the March Brown Mayfly.

 Updated: 5/18/2018; Authored By Staff Writer; Content ¬©www.InsectIdentification.org




The March Brown Mayfly adult is short-lived, but its very presence is a sign that the water is clean and the fish will be biting.



Mayflies are generally a good indicator of water quality. The early part of a Mayfly's life is under water, and they do not thrive in polluted streams, creeks, or other aquatic habitats. March Brown Mayflies are a popular food source for fish, especially trout, so anglers are keen to recognize them by appearance, behavior, and life stage. Such knowledge increases one's likelihood of catching fish by using a fishing lure that matches the present species of Mayfly.

Four general life stages are present in the March Brown: egg, nymph, subimago, and imago. Huge swarms form, usually over water, which have occasionally caused a commotion in more developed areas where people are not used to seeing them. After briefly mating in the air, females lay fertilized eggs at the water's surface. The newly hatched nymphs resemble crustaceans with large jaws. They search out slower-moving waters and feed for over a year until they crawl on land to molt into a more familiar winged Mayfly form. The early winged form of Mayfly is called a subimago by biologists, and a dun to anglers, and it is not able reproduce yet. Another molt produces the sexually mature adult, called an imago by biologists, and a spinner to anglers. A spinner gets its name from the circular swimming motion that results from flapping its wings on the water's surface. After laying eggs, females die and their bodies, almost transparent in water, float on the surface. Fish love eating Mayflies, and are very active during a spinner fall, when the Mayflies drop dead after reproducing. A swarm is an indication that some good fishing may be coming soon to that area.

March Browns and Gray Foxes were once considered separate species, and even differ a little in appearance, but they are now known to be the same. The Gray Fox form seems to develop after the March Brown form. Both forms are great for fishing. Though the adult lifespan of the March Brown Mayfly is short (a day), the presence of adults and swarms can last for a week as fully grown nymphs leave the water to molt.




Taxonomic Hierarchy
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Insecta
      Order: Ephemeroptera
        Family: Heptageniidae
          Genus: Maccaffertium
            Species: vicarium
Identifying Information
Scientific Name: Maccaffertium vicarium
Other Name(s): March Brown Dun, Gray Fox Dun, March Brown Spinner, American March Brown,
Category: Mayfly
Size (Adult; Length): 9mm to 16mm (0.35in to 0.62in)
Colorwheel Graphic Colors: brown, tan, black
Descriptors: flying, lights, swarm, congregate
Territorial Map
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Territorial Reach (A-to-Z)
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
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Alberta
British Columbia
Manitoba
New Brunswick
Newfoundland and Labrador
Nova Scotia
Ontario
Prince Edward Island
Quebec
Saskatchewan
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Mexico
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.