Black Mystery Caterpillars

Black Swallowtail caterpillar: 3rd instar

 When I brought the last of the fennel in, I cut the greens and put them in vases.   They're pretty, feathery things and look great with other cut flowers.

The other flowers got old and died and we noticed three little visitors happily munching on the fennel.  

These black caterpillars had hatched after we brought the greens into the house.  

Black Swallowtail caterpillar: 2nd instar

We decided to raise them until they turn into butterflies.   We've done it many times with monarch caterpillars, but it's been a few years.  

Of course, we wanted to know what they were, so we turned to our favorite ID site:  http://www.discoverlife.org/20/q?guide=Caterpillars

We searched and searched and couldn't find a match.  

So K2 insisted that we do a google search for caterpillars that eat fennel.

It was a smart tactic.   There is only ONE type of caterpillar that eats fennel.  Black swallowtails.   Unfortunately,   none of the pics we found of black swallowtails matched our little guys.    So we looked up the Wiki and discovered that this little guy really changes color as he grows.   

As caterpillars grow, they get too big for their skin and the shed it.   Each of these stages is called an 'instar'.    Black swallowtails look like our guys until the 5th instar, then they look a lot whiter and greener and stripier.  

At the end of the last instar, they curl up, anchor themselves and metamorphose into a chrysalis.  After a few weeks, they'll split that skin and out comes the butterfly.    Miraculous!

Moth caterpillars do not turn into chrysalises.    They spin a cocoon around themselves and metamorphose in that.