Canadian tiger swallowtail butterfly

Some years there are hundreds of these large, yellow and black butterflies flitting around in the spring.  This year, with the severe cold snap we experienced, there seem to be less of them.  That, however, just makes there appearance that much more special.

I have never found the caterpillar (click on this link to see one) which feeds on aspen, birch, and black cherry leaves.  The adult above is resting on willow leaves.  The adults take nectar from flowers, as do most adult Lepidoptera, 

The swallowtails generally overwinter by pupating in the fall and forming a cacoon called a chrysalis.  The chrysalis is attached to a branch and remains there until spring when the butterfly finishes metamorphosis and finally emerges as an adult.  So, how do the encased papae not freeze to death?  Antifreeze.

You heard me right.  The butterfly pupae produce ethylene glycol that lowers the freezing temperature of their blood.  Concentrations are high enough to prevent crystals from forming.  When the temperatures warm up, the butterflies emerge and begin the process of repeating the lifecycle.

Thanks for reading.

Eric Svendsen     www.ericspix.com