Saturday, March 22, 2014

Spring Has Sprung

"Cat" on a red hot napkin.
Spring has invaded out house in the woods.  The looper caterpillar above was on my napkin last night as we sat down to eat.  We used to call them inchworms but this one  measured close to 1.5" or 4 centimeters, so I guess it was a metric worm.

Caterpillars coming out of an egg are tiny and eat their way to full size.  This caterpillar is a member of the Geometridae family (Geo= earth, Metridae= measure).  It travels by fastening the hooks of its tiny prolegs on the rear segment to the ground, then extending its body as though looking around for the prefect perch for its 3 pair of front legs.  It was very confused by its surroundings as both of us were trying to figure how it got here.

"Anybody see a fresh leaf?  Where is the salad?"
While true legs work by muscles and joints not unlike ours in principle, the hind prolegs lack joints and extend and retract by pumping fluid into the structures inflating them like a long circus balloon.  Small hooks on the end, called crochets, hold on to almost any surface.

Crochets of a dagger moth larva-  Brigette Zacharczenko
Some geometrids overwinter as full grown caterpillars.  Our caterpillar hunting friend  Kevin Firth kindly searched out several possible ID's based on appearance and the trait of overwintering as caterpillars.  Hypagyrtis unipunctata is the most appealing to me as it is said to be very common, has been reported in Christian county and we are surrounded by its host plants - many trees, service berry and rose.  Unlike ticks which will freeze to death unless they get under the shelter of leaf litter, etc. these caterpillars actually hang out on tree bark and branches, freezing and thawing with the weather cycles.  They serve as a winter time snack for the golden crowned kinglet in Maine.*

The overwintering geometrid caterpillars start to roam just as buds open to provide fresh and tender leaves of their selected species.  The timing is critical for survival of the caterpillar and its predators.  Migrating birds depend on these early risers for food when little else is available.

Global warming or unusual seasonal temperature changes throws off the system.  This looper is out a little too early as the only buds opening around the house deep in the valley and away from the early sun are on a small clove currant, Ribes odoratum

Global warming also affects the forest nesting birds which feed on loopers when they first arrive at their seasonal home.  The caterpillars' emergence is signaled by temperature while bird migration is triggered by the length of the day and the number of hours of sun.  Without a phone app to warn birds of the disconnect, they have no way of knowing whether their cats are out of their bags.

Further information from the University of Wisconsin- Milwaukee.
* From one of my favorite books, Bernd Heinrich's Winter World.  He is a wonderful writer and has a number of books to choose from.

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