Attraction of moths to light

[Mark Walker]

As usual, this subject has produced an interesting and active thread.  I
don't have much to add, but while making my long commute through the woods
of Vermont last night, I illuminated what was an abundance of moths in
flight with my swerving headlight beams.  Actually, this was not a new
experience, as I see the same thing every time I drive in the evening
(although some nights there is more activity).

Last night was clear with a half moon or so, and the day had been hot and
humid.  What I realized though, was that other than my headlights and the
celestial light sources, there was very little light to be seen.  And yet,
many, many moths were enroute to someplace.  The fact that they were seen
was purely accidental.  They were not attracted to my headlights, but were
simply revealed by them.  I say this because the direction of flight was
perpendicular to the direction of the light beams, and no change in flight
direction was perceived.  The moths were "crossing the road" in a similar
manner to the beaver, porcupine, raccoon, fox, deer, and moose.

They were going somewhere, and I don't think it was to someone's porch
light.

I suspect that the moths that come to congregate around our light traps are
exhibiting an exception to normal behavior.  We recognize it as "typical"
moth behavior, because we only get to observe them under our lights.  But
the vast majority of moths are out there, enroute to someplace that doesn't
emit light at all (at least not within our visible spectrum).  Could it be
that whatever cues are used for reproduction are somehow mimicked by our
lights?  Could it be that even the celestial light sources tend to
interfere with this, and that their activity is enhanced on cloudy nights
(only to be further confounded by a porch light)?  Could it be that I'm all
wet with this?  Yep.

Anyway, moths are apparently quite active and willing to fly potentially
long distances without the need of (or the desire of) a lamp.  It's a bit
tough to say for sure what they're doing, since as soon as you put your
flashlight to the task, you've contaminated the data.

Mark Walker
Castleton, VT.