An online resource based on the award-winning nature guide – maryholland505@gmail.com

Moose Flies and Moose

My recent quest for finding moose was successful – and my most striking observation, other than their imposing size, was the presence of a multitude of flies on and around the hindquarters of every moose I saw. I assumed they were deer flies, but they didn’t appear to be bothering the moose and research revealed that, in fact, they were moose flies, Haematobosca alcis. These flies can be seen throughout the spring and summer in dense swarms over and on the rumps of moose — five hundred or more may accompany a single moose. Unlike most other biting insects, both male and female moose flies feed on their host’s blood. Although not considered a serious pest (moose tend to pay little attention to them), moose flies may be responsible for sores often found on the hind legs of moose. It is thought that female moose flies may be stimulated by gases released by the moose when it is defecating, after which the female flies descend and deposit eggs into crevices in the moose’s scat.

6 responses

  1. Susan Holland

    What a fantastic photograph – and I had never heard of moose flies, so it was (as always) something new for me to learn. I think you should take more photographing trips to Maine!

    June 11, 2012 at 3:21 pm

  2. Kathryn Connell

    Poor thing. It makes me itch just to see the picture.

    June 11, 2012 at 5:13 pm

  3. What’s the thing on the front of her neck?

    June 11, 2012 at 5:55 pm

    • It’s a long, dangling flap of skin referred to as a “bell” or “dewlap,” usually larger in males than females. Bull moose use their dewlaps as a means of communication. After soaking it in their own urine while lying in a moose wallow during rutting season, a bull will rub the cow with his chin (“chinning”) and the dewlap transfers this bull’s scent to the female. The size and shape of the dewlap may also be an indicator of dominance to other bulls, just as the size of antlers is. I am not sure what function it has for females.

      June 11, 2012 at 8:36 pm

  4. Sarah Morrison

    So gross, but so neat!

    June 11, 2012 at 10:22 pm

    • Hi Sarah,
      I agree! I had the best time in Bridgton, thanks to all your hard work. Many thanks for getting the word out. What friendly folks you live amongst! Mary

      June 11, 2012 at 11:32 pm

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