the mystery of Vanessa unidirectional migration
Mark Walker
MWalker at gensym.com
Wed May 2 17:49:53 EDT 2001
Hmmmm. Of course, even dispersal in "all directions" would appear from a
particular position to be unidirectional. The movement wouldn't exactly be
random from every position, as the bugs would be moving away from where they
were coming from - wherever that may be. Sort of the same as magnetic lines
of flux - anwhere away from the poles.
The swarms we spotted in Rancho Cucamongo on April 24 were incredible. They
appeared like swarms of locusts - numbered by the hundreds per square meter
- flying about 50 feet above Interstate 15 in a continous stream. They
looked like big black snowflakes. I've been watching the bug in this
spectacular dispersal for about three months now, but never have I seen
anything like I did a week ago. All in the car commented that it looked
like something from a Alfred Hitchcock film - an invasion of sorts like
something out of a 50's B-rated horror film. The leps were flocking in
these hordes up high enough to avoid mass destruction from oncoming traffic.
They appeared to moving north - towards Cajon Pass. I'm sure the phenomenon
was a significant nuisance to the residents of the Inland Empire.
We've also seen a good number of mating adults over the past few weeks.
Mark Walker
Oceanside, CA
> -----Original Message-----
> From: Liz Day [mailto:beebuzz at kiva.net]
> Sent: Tuesday, May 01, 2001 10:43 PM
> To: leps-l at lists.yale.edu
> Subject: Re: the mystery of Vanessa unidirectional migration
>
>
> >Although the mass of individuals move out in one direction
> (in this case
> NE.....) some individuals move out in all directions, even S.
>
> "All directions" is what I would expect if the species is
> simply dispersing
> and has no intention of returning before winter. Right? It
> would make no
> sense for it to disperse primarily or preferentially
> northwards, if that
> direction leads to places its offspring (or their offspring,
> or theirs) are
> doomed to never return from, unless the survival prospects
> from moving
> east, west, south, or at random are even worse, which I would
> take some
> convincing to believe.
>
> Ron says,
> "Other comments and thoughts?"
>
> Yeah. Am I understanding correctly that red admirals and
> painted ladies
> never overwinter in the north as pupae, only as adults??
>
> Cheers,
> Liz
>
> Indianapolis IN USA
> Where we are getting plenty of birds and bees but not that
> many moths yet.
>
>
>
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