|MadSci Network: General Biology|
Genevieve, A very unique observation about the flies in the middle of the the Great Lakes. I am not too sure of your identification of the species of fly - because it sounds like you are describing a larval aquatic fly such as a certain 'midges'. This would explain why they occur in swarms, and many kilometres away from a solid land mass. These flying insects likely emerge from their aquatic life stage when the conditions (temperature, time since hatching, etc.) are right, which is not always in what would look to be an ideal location. But many species of insect can rest on the surface of the water - partly because of their tiny mass and partly because they may have body and leg hairs that increase their surface area and make it more likely that they can make use of the natural surface tension of the water. The apparent lack of food in the middle of a lake may not be an issue for this species - as the adult form of many insects do not feed (many don't even have mouth parts) - the sole purpose of this lifestage may be to reproduce. I am curious to know if these insects are biting the people in your sailboat. I would suspect that they are not (which confirms the lifestage hypothesis), and if they are only interested in reproduction these insects may be using you and your boat as a reference point for the swarm. Several species of insect use a strategy called 'hill-topping' where they congregate together on the tallest object around. This helps form a mating swarm (which increases the likelihood of any individual meeting up with a member of the opposite sex - especially given a space as vast as an open lake). And this would explain the behaviour of the swarm if it seems to be following your sailboat on a fairly calm day. Very interesting stuff... Keep up the astute observations! Compiled with the expertise of Rod Hallum, Entomology Technician, University of Western Ontario, London ON. -Neala MacDonald Genevieve Hanna wrote: > Hi Neala > > Thank-you for the reply about the flies in the middle of lake Ontario. > > I would to add some points... > > Yes they do bite, and they look just like a common house fly but they > are very slow and sluggish we can actually catch them with our bare > hands. In addition when we kill some we can observe other flies > gathering around the dead fly and I suspect they are feeding? > > I think you do wonderful work and thanks for your patience > > Yours truly, > Genevieve Hannah
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