[NatureNS] kelp flies/photography

Date: Fri, 23 Feb 2007 13:45:35 -0400
From: David & Alison Webster <dwebster@glinx.com>
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Stephen Shaw wrote:

> Regarding the comments
> about the thermally protected micro-environment in the air spaces 
> under stuff
> like washed-up seaweed, fully agreed, but not in the case of the 
> adults if they
> come out and cavort on the snow where their bodies will rapidly 
> equilibrate to
> ambient temperatures (probably in seconds).  So could it be that these 
> are
> simply occasional doomed escapees 

Hi Steve & All,            Feb 23, 2007
    In the case of insects with legs sufficiently long to keep the body 
well above snow level, I would expect on calm sunny days significant 
warming by reflection of sunlight from snow.

    That being said, the massive reproductive potential of the typical 
insect shows that most individuals must come to grief before reaching 
reproductive age and getting stranded on a snowbank in brisk weather is 
no doubt one way to do so. At the very least they would be a sitting 
duck for any insectivore that came along.

    From about now on, when stumps of recently cut hardwoods start to 
bleed on sunny days, one will usually see flies of several stripes, that 
presumably overwinter as adults in some nearby cold corner, feeding on 
the sap.

    Some flies are relatively tolerant of cold. In December, 2001 I 
found some crane fly larvae in debris on polyethylene that was on top of 
a woodlot woodpile and brought some home to a woodpile in the yard where 
they spent the winter well above the protection of warm snow or warm 
soil. They wintered well and adults emerged sometime after June 5.

    In a related vein, I wonder if the sometimes profuse complement of 
bristles, hair or wool may reduce heat loss during flight or while 
landed in windy weather, by decreasing air flow near body parts.

Yours truly, Dave Webster, Kentville
   


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