Caterpillars

When I was going through my photos to update the blog, I was amused to find that the images were about 25% baby photos, 25% photos of everyone and everything else, and 50% caterpillars.  Elsa and Nora were given some Imperial Moth caterpillars when they visited my parents in August.  At first we thought, "What cute little black, spiney caterpillars!  We'll watch them for a few weeks until they turn into little moths!"  But they changed colors and kept being caterpillars for a very long time and soon were not very little at all, so I finally did my research.  Imperial moths can be the size of your hand!  And take all winter before they turn into months in the spring/summer!  

After passing through all 8 instars (when the caterpillars shed their skin so they can grow larger) the caterpillars were 4 inches long and eating a small branch of leaves every day.  They were rather high maintenance pets, but, as you can tell from the amount of photographs I took of them, I was absolutely fascinated with them.  I don't have any photos of their very first instars when they were still black, but you can still see how they change a bit between these last few stages.  

Once they start on a type of host plant for food, they will only eat that particular host plant for their whole life, so there's not much left of the red oak in the brush in back of our building!

We caught this one in action shedding it's skin and beginning the last instar.  It will get darker orange-brown as it fills out it's new skin. 

Ok, so I hope this is not too much information, but as I said, I found these creatures fascinating.  After I took this photo I realized he was pooping!!!

They were green inside!

And they don't even have to stop eating!  Their back "panels" were harder than the rest of their body and closed up tightly when it was all done.

Their patterning was beautiful.  I read that the Imperial Moth caterpillars can be orange, brown, or bright green - ours were all orange.

By the time they were fully grown (in a little less than two months) you could hear them biting and crunching the leaves in the adjoining room.

Imperial Moths are a bit unusual because the caterpillar does not make a cocoon.  Most moths spin a cottony, silky web sack around themselves in which they then make a pupa.  Imperial moths instead burrow in the ground and form a pupa without a cocoon around it.  Sure enough, one day we found that one of the caterpillars had come down from the branches and was working his way into the soil in the bottom our the bucket.

I'm a rather nosy scientific observer, so I kept checking on them under the soil.  In a few days we found one had just wiggled out from his old skin:

The pupa was brand new and rather soft still so we were very careful, and it would twitch and wiggle when touched.

By the end of the day the vibrant yellow-orange hardened into a much safer brown-black:

They still twitch when gently poked, and I'll keep checking on them throughout the winter.

So there's your biology lesson for the day, and I'll post an update next year when they emerge if we manage to keep them alive through the winter.