Wednesday, August 7, 2013

Alianthus moth

Moth with toothpick to compare
Moths are supposed to be dull, right?  Someone forgot to tell the ailanthus webworm, Atteva  aurea.  We regularly find these small moths on the wall outside our deck door, drawn by the spotlight.  They would be better know if they were larger.  This one was attracted to the light at the FOG All or Mothing event at Bull Mills.

Chris Barnhart relates that it had no common name at the turn of the century.  Its range was restricted to Florida, spilling over some into the Gulf states and southward, feeding on native plants in the Simaroubaceae family.  These are predominately tropical trees and shrubs with one-seeded winged fruit and bitter bark.  The primary host was the Paradise Tree found only in southern Florida down to northern South America.

So why are they commonly found in the Ozarks and along Bull Creek?   We moved them north, more or less, by importing Ailanthus, the notorious invasive Tree of Heaven we described in a past blog.  This Asian import, brought to North America in a misguided effort to raise our own silk worms, is a member of the Simaroubaceae.  It spread widely with no significant predators and little regard for Northern climate.  The Atteva  aurea webworm found it delicious and has successfully chased it across the continent, to a degree that it achieved its new common name, "Ailanthus webworm".

Ailanthus webworm- Photo by Auerilas
It does not tolerate cold winter and migrates each year from warmer climes.  I suspect that our recent mild winters have contributed to their increased frequency.  They lay eggs in a nest of several leaves pulled together by a web of silk.  The caterpillars then eat the leaves of the Ailanthus, although not sufficiently to impair the spread of the trees.  We have only seen the Tree of Heaven once in our valley, but there are likely more in the woods growing undetected.

 Chris notes another weird thing about the moth is that some of them appear to have just 4 legs, like the one he photographed at the top of the page, while others have 6 legs.  Of 283 specimens pictured on Bugguide, only 4 show 6 legs.

In addition to being colorful model for macro photography, they are pollinators to a number of flowers.  And anything that eats a Tree of Heaven, however little it may be, is a friend of mine.
See also the discussion in the Mobugs blog.

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