Vanessa at night - no 3

Woody Woods woody.woods at umb.edu
Sun Feb 3 10:53:12 EST 2002


Stan and others, regarding the suggested experiment, perhaps another way would
be to work with marked butterflies in a walk-in cage, monitoring their
position 2-3 times through the night. If the butterflies are flying at night,
this would allow directionality of movement to be established. Colleagues have
done cage experiments with migrating butterflies in Costa Rica (crepuscular
behavior though, not nocturnal) and have found cage movements and activity
corresponding to outdoor observations.

I have found Vanessa occasionally-- not often-- flying in an indoor walk-in
cage during the night portion of a 16L:8D light cycle, at a temperature of
around 21 decrees C. Those observations are at this point just anecdotal,
though. 

Monitoring activity of caged animals has contributed to understanding of bird
migration in a number of classic works. 

I guess I'd be concerned that in an outdoor experiment a butterfly could crawl
out and then be taken by spiders or something else-- a problem I had even with
some cage experiments when plants were in the cage. Often the remaining bits
were scattered. However, doing BOTH outdoor caged and cageless experiments
could be pretty strong. 

Also, it is certainly true that the eyes of nocturnally flying moths are have
the capacity to dark-adapt, with consistent physiological changes following a
circadian pattern (articles by Richard White and Ruth Bennett), and a logical
research step would be to ask whether the eyes of Vanessa and other suspected
nocturnal migrators have the same capacity. 

Woody Woods

Stan Gorodenski wrote:
> 
> Paul Cherubini wrote:
> >
> >
> 
> Of course, the biology of the butterfly would have to be taken into
> consideration.  What I suggested is not a completely worked out
> experimental design, nor was it intended to be one.  If your observation
> regarding the Monarch translates to Vanessa, then the absence or
> presence of the butterfly would not be monitored throughout the night
> but just once, no later than one hour prior to sunrise.
>  (snip)
> 
> > With regard to butterflies flying at night, here is a response
> > from Dr. Chip Taylor I found on the Web:
> >
> > http://www.monarchwatch.org/read/faq4.htm#29
> > 29. Why don't the Monarch butterflies fly at night?
> >
> > Dr. Chip Taylor replies:
> >
> > "Butterflies are diurnal insects which means they only fly
> > during the day. We are not aware of any butterflies
> > that fly at night. Why this is the case is not clear, but
> > butterflies are generally brightly colored and highly
> > visual and their eyes are not designed to function
> > under low light conditions. Moths are predominantly
> > nocturnal (night flying) and they have what are known
> > as "dark adapted" eyes which allow them to fly at night
> > when light levels are extremely low."
> >
> 
> 
> 
-- 
*********************************************************
William A. Woods Jr.
Department of Biology
University of Massachusetts Boston
100 Morrissey Blvd                      Lab: 617-287-6642
Boston, MA 02125                        Fax: 617-287-6650
*********************************************************

 
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