Tuesday, June 30, 2009

Ch-ch-ch-changes

stage3

I've been reading up on swallowtail caterpillars. Did you know there are five different caterpillar stages (called instars)? I didn't. I knew there were four developmental stages going from egg-caterpillar-pupa/chrysalis-butterfly, but I didn't know there were five sub-stages within the caterpillar stage. I kept wondering how all the different-looking caterpillars I found through Google Image Search could be the same species!

During the first and second instar stages, swallowtail caterpillars are dark brownish-black with yellow-orange spots, black spines and a white band around their middles. I saw some of these, but didn't get any pictures. I hope I get another chance to show them to you.

In the third, fourth and fifth instars, the caterpillars turn various shades of yellow, cream and green. I suspect the photos from yesterday are third instar caterpillars and today's photo is a fourth instar. Fifth instar is a pre-pupa stage, just before they form a chrysalis.

How do caterpillars go from first to fifth instar? They molt (shed their skins), just like a snake! Birdchick has some great information on her blog, including a video of a molt and pictures of caterpillars in various instar stages.

4 comments:

  1. Caroline,
    I'm so disappointed, we have not had a single butterfly in our garden this year and I have only seen one humming bird. Where are they? I'm glad that you are able to enjoy them. :-)--Randy

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  2. Randy, we've had more caterpillars than butterflies and we've only had two hummingbirds. Perhaps it's too hot for the hummingbirds to hang around here. We usually get butterflies later in the summer.

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  3. Very interesting post. I try to keep fennel around for the butterflies--the caterpillars have mowed it to the ground this year!

    I think we have the areas hummers in our garden! I have counted 8 all vying for the same feeder! Yesterday one staked his claim on it, sitting on it and chasing away all the others. More fun than watching TV!

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  4. I have several on my parsley plant and must heck which stage they are at. I would love to see them pupate. Thanks for the information.

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