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From: kuento@kuhub.cc.ukans.edu
Newsgroups: sci.bio
Subject: Re: moth flutter
Message-ID: <28979.27d6f9fb@kuhub.cc.ukans.edu>
Date: 8 Mar 91 08:42:02 GMT
References: <1991Mar5.195259.20804@xn.ll.mit.edu> <2879@beguine.UUCP>
Organization: University of Kansas Academic Computing Services
Lines: 32

> I heard a long time ago, that the movement of moths overall is not random.

That's correct - in fact, there are no self-propelled organisms in
which movement is truly random, except for certain "escape" behaviors
in various organisms (that is, random movement is only a temporary and
very special condition). Even bacteria do not move randomly.

> address.  That the overall movement is directional can be shown by the way
> moths are attracted to lights at night.  Supposedly the reason for this is
> that the moths have some sort of guidance system which relies upon
> parallel rays of light.  With sunlight or even moonlight, this is a pretty
> good approximation since the lights are relatively far away.  With an
> artificial light though, the light rays are NOT parallel.  The moths
> however don't realize this and as a result spiral in towards the light
> source.  Does anyone have any information on this being true or not, or
> are moths just attracted to bright lights for some reason?
>      -Andy
 
Moths and many other insects are attracted to bright lights because
they try to keep the light *above* them as they fly (this is normally
where the moon will be in their field of vision). Artificial lights
are disorienting because when the insect shifts around so the light is
"up" in its field of vision, it ends up spiralling in. If you ever
look closely at a moth circling, you'll notice that the moth is
tilted strongly sideways, perpendicular to the long axis of the light
source. If it were simply being confused by parallel vs. non-parallel
lights, only the yaw would change, not the roll, and they would circle
while remaining essentially level.
-------(please include "DY" in subj header of mail to this user)--------
Doug "Speaker-To-Insects" Yanega      "UT!"       Bitnet: KUENTO@UKANVAX
My card: VIIII The Hermit  (Snow Museum, Univ. of KS, Lawrence, KS 66045)
"Bleating and babbling we fell on his neck with a scream" - P.F., Animals