Vanessa at night - migrations

[Rudy Benavides]

Some say its possible, some say no.  Here's an interesting read (with 
references given)about Monarchs crossing the Atlantic.

[[ Indeed, in the past, Monarchs have been reported (by pilots) on height 
levels of about 1500 m. The 'weak' point remains the question where they 
have been at night. During the yearly southerly remigration of Monarchs from 
Canada to Mexico, Monarchs normally don't migrate during the night, but 
roost together in trees. However, Williams (1958) and Ross (1993) suggested 
that under certain conditions Monarchs are also able to fly at night, 
especially during warm nights when temperatures do not urge the butterfly to 
become inactive. Brower (1995) suggests that migration across large water 
masses like oceans is merely possible thanks to wind-assistance and 
hitch-hiking on ships, e.g. during the non-active periods. Although several 
occasions are described when Monarchs have been seen landing on the 
water-surface and after a while taking off again, Brower (1995) states that 
resting on the watersurface for longer than a few minutes would be lethal to 
the butterfly and is probably not the explanation for what Monarchs do at 
night when crossing oceans.
Previous to the period of suspected migration across the Atlantic the 
following observations at the East Coast of the USA were obtained from Dick 
Walton (pers.e-mail). At Cape May, New Jersey, his research includes 3 daily 
Pollard-type transects of approximately 5 miles each. The seasonal average 
for Monarchs per hour of censusing in 1995 was about 26. Daily averages 
during the suspected migration period were (Danaus plexippus per hour):
Sept. 26 - 15.79
Sept. 27 - 26.00
Sept. 28 - 69.31
Sept. 29 - 32.54
Sept. 30 - 36.21