the mystery of Vanessa unidirectional migration

Mark Walker MWalker at
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]
> Sent: Tuesday, May 01, 2001 10:43 PM
> To: leps-l at
> 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.
>  ------------------------------------------------------------ 
>    For subscription and related information about LEPS-L visit:


   For subscription and related information about LEPS-L visit: 

More information about the Leps-l mailing list