Vanessa at night - migrations

[Paul Cherubini]

Stan Gorodenski wrote:

> From Orley Taylor's work on the magnetic effects on Monarch orientation, it
> would appear that Monarchs could successfuly migrate at night, even if
> they may be blind.

Yes Stan a few years ago Dr.'s J.A. Etheredge, Orley (Chip) Taylor and
two other insect behaviorists published a fantastic new finding:

"Monarch butterflies (Danaus plexippus L.) use a magnetic compass
for navigation." in the Proc. Natl. Acad. Sci. US 23 Nov 99 96:13845)

The news of this fantastic "discovery" also circulated
throughout the popular press .  However, four months later
the authors RETRACTED their paper. Predictably, this retraction
didn't get much press coverage so perhaps you never heard
about it.  Here are the details:

http://scienceweek.com/2000/sw000602.txt
MONARCH BUTTERFLY MAGNETIC COMPASS PAPER
RETRACTED
      
This is a cautionary tale, an example of how the extraordinary
complexity of biological organisms, systems whose
operating variables are often unknown, can lead researchers
astray.

In November 1999, a research team (4 authors at the
University of Kansas Lawrence, US) reported that fall migratory
monarch butterflies, tested for their directional responses to
magnetic cues under three conditions, amagnetic, normal, and
reversed magnetic fields, showed three distinct patterns: In the
absence of a magnetic field, monarchs lacked directionality as a
group; in the normal magnetic field, monarchs oriented to the
southwest with a group pattern typical for migrants; when the
horizontal component of the magnetic field was reversed, the
butterflies oriented to the northeast. In contrast, nonmigratory
monarchs lacked directionality in the normal magnetic field. The
authors suggested the results were "a direct demonstration of
magnetic compass orientation in migratory insects."

Four months later, in March 2000, the authors retracted
their paper, noting the following: "The positive response to
magnetic fields in two experiments cannot be repeated. Further
experiments show the false positives in these tests result from a
positive [directionality of movement (taxis)] by the butterflies
to the light reflected off the clothing of the observers. We
therefore retract our report. We regret the inconvenience that
publication of this study may have caused."

 
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