Caterpillar Diary — September 28

This is the last 0f 4 posts about the little red-spotted purple butterfly’s caterpillar I found in one of our wild cherry trees.

The caterpillar rested on the leaf last night. I used a flashlight to get this picture. It has the leaf shapes cut out that will become its hibernaculum where it will spend the winter.

I found the caterpillar in its hibernaculum early this morning. I had hoped I could watch more of the process, even though I knew they worked mainly at night. Its shelter measures 3/8 inch long and the overall length is 3/4 inch.

I always thought the caterpillar backed in, but apparently it doesn’t.

Next trip out I found the caterpillar eating on another leaf, looking like it was going to make another hibernaculum. Was the first one  uncomfortable? Was the caterpillar bored? It hasn’t returned since, so maybe it was hungry?

This picture better shows the back end of the caterpillar. The caterpillar is less than 1/2 inch long. I’m estimating its size, not wanting to disturb it anymore than with my presence.

The caterpillar hasn’t come out again since this picture was taken that I know of.

Look close at the base of the leaf stalk, and you’ll see where the caterpillar used silk to bind the leaf to the branch to prevent it from falling off during the winter. It covered the top of the remaining leaf pieces with a sheet of silk. The silk shrunk and dried, curling the leaf in the process.

Now, imagine the caterpillar spending the winter in this shelter, through the possible below-zero temperatures, snow storms, ice storms, not eating. They go into diapause in which their development stops This gets into a chemical explanation. It’s one of those things I find amazing and don’t completely understand how it’s possible. Some butterfly species overwinter as adults, some as chrysalis, others as caterpillars and the rest in their egg.

 Red-spotted purples usually start flying in May here in southern Illinois.

They are closely related to the viceroy butterfly. Their caterpillars closely resemble each other, and each can be either green or brown. Most of the red-spotted purples I’ve seen are brown. Patterns of both caterpillars mimic bird droppings.

Viceroy butterflies mimic the monarch butterfly, except for an extra black band on their hindwings that the monarchs don’t have.

Both red-spotted purples and viceroys are in a family of butterflies known as brush-foots. Their front pair of legs are greatly reduced to where they look like they only have 4 legs, instead of 6. Besides flowers, many of them feed on rotten fruit and at sap flows.

 With any luck at all, this little caterpillar will survive and I can watch its development to adult in the spring.


3 responses to this post.

  1. Posted by Therese on October 7, 2012 at 10:27 am

    Whew! Get my thesaurus out! I’m tired of using the same words over and over…”amazing, unbelievable, Wow, interesting, super,” etc. etc.
    To think that someone takes the time to observe, even the smallest of God’s creatures, is rare. You do it sooooo well! You help others appreciate beauty in everything…no matter how big…no matter how small. You are a true naturalist! The world is graced by your presence. The mere words “thank you” do not seem enough. But…here goes anyway…thank you, Kathy!!!


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