Red Admirals Migrating through Iowa

[Monarchrst at aol.com]

In southern Arizona we have had a major migration of Painted Lady Vanessa 
cardui (L.) going on almost continuously since April 11, 2001.  The first and 
smaller peak was on Thursday, April 12 with 20-25 per minute passing across a 
20-yard stretch of my driveway.  The day was clear, calm and sunny, maximum 
temperature was 75 F, and the butterflies were traveling roughly in a 
south-east direction, presumably from the big hatches going on in our own 
lower deserts in Arizona.  Over the next week or so the numbers became less 
and the direction of the butterflies gradually changed to a north-north-west 
direction.

This week we hit one of the biggest migrations I have seen here, that peaked 
on Monday, April 23, and for several hours the number crossing the same 20 
yard stretch of driveway increased to a staggering 200 per minute that day.  
All traveling in a north-north-west direction.  That number was sustained for 
almost the entire day.  Even today we were reaching numbers of 40-50 per 
minute but today their habits were changing and instead of unwaveringly 
flying in one direction, many more were stopping to nectar on any flowering 
plants, shrubs or trees they could find.  Again the days were clear, sunny, 
calm and hot.  Maximum temperature on Monday was 86 F and that had increased 
to 99 F by this afternoon.

Motorists were finding difficulty in driving due to the squished bodies on 
their windshields and all vehicles with radiator grills had almost a uniform 
covering of bodies and wings plastered on their front surfaces.  The 
television, radio and newspapers have all taken to brief articles on the 
phenomenon.  A few weeks ago the same media were talking about the hundreds 
of mature cardui larvae that were troubling many of the homeowners on the 
desert edges.

This spring we had significantly more rain than normal at exactly the right 
time to trigger massive plant growth in the deserts and many areas have been 
totally covered in spring flowers, now mostly drying out.

Ian Watkinson, Yuma, Arizona.

 
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