Wednesday, September 19, 2012

Polyphemus Caterpillar & Cocoon

Many, many thanks to Maggie McCartney and Thomas Waser in our Herpetology Department for spotting this incredible caterpillar on our Museum grounds!  It's a polyphemus caterpillar--my index finger is shown for scale.  And, yes, the caterpillar really is almost a neon green color.  I took these photos on September 15, 2012.
I usually take my camera with me everywhere I go since I never know when a great photo opportunity will turn up.  And wouldn't you know it--this was one of those rare days I didn't bring my camera with me!  Fortunately, I was able to put the caterpillar in my empty lunchbox and took it home with me.  At home, I immediately started photographing to take advantage of the day's remaining sunlight--it was the only way to do justice to the brilliant green color!  This side view shows the caterpillar walking along a stick:
The first three pairs of legs closest to the head are the "true legs" or thoracic legs.  The more fleshy looking legs are "prolegs"--the middle four pair are the anterior prolegs and the last pair are the anal prolegs.  The next photo shows the contrast between the thoracic legs and prolegs:
Here'a an even closer look at the prolegs.  You can see that each proleg ends in a flat pad rimmed with small hooks called "crochets":
It was fascinating to watch the superbly choreographed movements of all the legs--it made the body seem to undulate or ripple:
Here's a close-up of the head with the mouth parts closed.  The two slender finger-like projections to the side of the mouth are the antennae:
Here's the mouth open--kinda scary, right?:
Do you see a small cluster of five dark dots on the side of the head?  These are simple eyes called "stemmata."  There's a sixth simple eye positioned close to the base of the antenna, making a total of 12 simple eyes on the caterpillar's head:
Some characteristic markings of the polyphemus caterpillar are the bright slanting yellow lines along most of the middle segments, punctuated by silver and reddish "warts."  You can also see some very fine hairs:
After I finished with the above photos, I put the caterpillar in a small container with some paper towels on the bottom.  I figured I'd download the photos first to see if they turned out clearly before releasing the caterpillar in my backyard.  To my surprise, an hour later, I found the caterpillar beginning to make its cocoon!  In the next photo you see the back end of the caterpillar--the dark lines form the anal plate.  At this point, its body was already stuck to the paper towel:
In the next shot, look carefully and you can see some silk strands.  These strands are usually used to help anchor the caterpillar into a leaf.  It will draw the sides of a leaf together and then spin its cocoon.  In this case, it used what was on hand--the paper towels!  I trimmed the edges of the paper towel to give it a more leaf-like shape, and when I checked on it later in the evening, it had finished its cocoon:
So now what?  If I'm lucky, perhaps by May of next year it'll emerge as a beautiful poyphemus moth.  If it survives, I'll post the photos.  For now, in order to help regulate natural temperature, the cocoon is sitting in a large container in my garage, waiting  for spring....

And, it seems my cocoon wasn't the only one found on the Museum grounds!  Horticulture staff member Darl Fletcher and educator Judy Molnar pointed out yet another polyphemus caterpillar making a cocoon--this one in the leaves of a tropical milkweed plant located in our horticulture support area.  I was able to get a shot of the face, with the bright yellow line on the first thoracic segment, and also a detail of those lovely silvery "warts" and finally a look at the caterpillar as it began to draw leaves around itself to make the cocoon--do you see the fine silk strands?:
Finally, here's what its cocoon looks like a day later:
More "off the beaten path" in two weeks....


  1. Did your caterpillar come out in May? I teach a preschool class and we just found one who also made a cocoon. I'm really hoping we can keep him alive until May because we are planning to read the Very Hungry Caterpillar in May.

  2. Hello Bill & Shannon, Yes, the moth did emerge from the cocoon! Please check out the "Polyphemus Moth Update 2013" I posted on May 29, 2013--pictured there is a female. In "Spring Things 2013" posted on May 15, 2013, the bottom pictures show a male--note the "feathery" antennae. These moths usually emerge during the first humid, warmer days in late spring (around May.) They only have about a week to live--their primary goal is to mate, so they don't eat. If you have one emerge, release it in a quiet, protected spot outside--it will probably fly off at nightfall. What an amazing educational opportunity for your pre-school kids!...and Very Hungry Caterpillar is one of my favorites, too...Cheers, Lisa