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From: Matt Broze <mkayaks_at_oz.net>
subject: Re: [Paddlewise] Yum-yum yellow -- bug attractant? (Moth flame thread)
Date: Tue, 11 Jul 2000 22:57:23 -0700
NEWTOT_at_mail.modot.state.mo.us wrote:
<SNIP>
>>I also notice the increased presence of bugs when I use my headlamp at
night -
it's like a beacon to the bug world!  I hate to give away my location just
because I need to see what's ahead.  Wish I could afford night vision
goggles!<<

My understanding is that the brightest light, to a moth and some other night
flying insects, is taken to be the moon and is used as a distant fixed
object in which to navigate in a straight line (by keeping it at the same
visual angle). Since your headlamp is a "beacon" much closer than the moon a
moth flying by it (with it in its forward quadrant of vision) will naturally
spiral into the light trying to hold the angle constant. You will also
notice that sometimes moths spiral out and away from lights. They are trying
to hold it fixed in a rearward quadrant of their visual field. This is kind
of off topic so let see if I can make it more relevant to keep the list mom
happy.

A kayaker in fog could likewise be confused by a nearby sound that sounded
more distant than it was. He could easily circle the sound (if ignoring the
compass or GPS). I once circled a small island I was wanting to travel along
because I knew a spit pointed where I wanted to go, into the bay of the next
island. Unfortunately the spit was covered by high tide and so we didn't
realize we were circling the island until we came upon the landmark we had
first sighted (after navigating directly to it after a six mile crossing by
compass and compensating for the winds and currents). For a few minutes we
thought we were pretty hot stuff finding that little island in that thick
fog after six miles. We then ignored our compasses and tried to navigate
using the nearby island (remember the moth). While circling the island we
didn't even recognize the true cause of the sudden change in current
direction. It even took us a few moments to realize that the tower (that
shouldn't have been where we thought we were) was actually our first
landfall.  That sure took the wind out of our overblown sails.

Fog really throws off distance perception as well. I can recall seeing
breaking waves in an overfall in fog and because they were so much nearer
than they looked to be I took them to be several times larger than they
turned out to be.

Anyway, the bugs don't like your light, it is just another form of human
interference with nature (providing an unnatural light). The resultant
navigational error it causes can burn the moth on the flame.


Matt Broze
http://www.marinerkayaks.com


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