Thursday, September 2, 2010

Tiger Swallowtail

Caterpillar- Matt Boehner
A while back, Matt Boehner sent me a picture of a larva his dog had coughed up.  It had a funny bluish tint (you would probably too if you had been coughed up by a dog) but its markings were typical of an Eastern Tiger Swallowtail larva.  I used Photoshop to adjust the colors to that of the grass, getting it closer to a true color. 

 Early Instar-
Tiger Swallowtail larvae change dramatically in appearance as they develop.  The larvae go through four molts, called instars, before they reach full size and form their chrysalis.  The early instars look like "bird poop" while the final instar is bright green with "eye" spots.  See this page for examples.

Fourth Instar-
When a caterpillar is fully grown it wanders away from feeding on its host plant in search of a suitable pupation site.  It frequently darkens during this stage as seen by Matt.  This darkened brownish color is probably more protective as it leaves its green leaf perch to attach its chrysalis onto something more substantial like a gray twig or bark.

Eastern Tiger Swallowtail
Color is in the brain of the beholder- who knows if one person’s blue is the same as another's?  Wavelength is real, so you can always count on a spectrum from sunlight for an objective check.  The problem is that you can’t rely on cameras and computer screens to reproduce it accurately, at least not without a lot of attention to detail.

The idea that we don't share the same descriptions of colors has led biologists to develop color comparison charts.   Robert Ridgway's color standards for bird identification might save my marriage.  Barb and I are always arguing over what is blue or green.  Perhaps you have a similar spousal story- if so, spare me as I have enough trouble correcting my wife.

For information and pictures go to this site.
Addendum:  Matt reports that it formed a chrysalis.  I was afraid after its dog-gone experience it would be "too pooped to pupate."

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