Ctenucha virginica caterpillar and adult

2012 April 18

We just caught another one of these over the weekend, so it is probably time to post this.
On May 21, 2010 Sam and I found this hanging on the side of my father-in-law’s hunting blind in our back yard. I recognized it as a caterpillar that I’d originally posted way back in 2008, but hadn’t reared to adulthood to positively confirm what it was.

Oh, sure, I said at the time that it was probably the caterpillar of a Ctenucha virginica moth, which I had photographed and posted the year before that, but that was conjecture. I craved proof.

This one stayed unrolled a lot better than the 2008 specimen, so I was able to get pictures of its orange-and-black face;

its mouth;

and its orange-brown prolegs.

So, to raise it, we popped it in a jar with some grass (which is what they are supposed to like to eat), although I didn’t expect it to eat much. It seemed likely that the reason it was on the wall of the blind was that it was looking for a place to make a cocoon. And sure enough, that was what it did within a day or so after we found it:

The cocoon looks to be composed about equally of the caterpillar’s hairs, and enough silk to hold them together. The hairs are stiff and irritating to the skin (and presumably, to the mouth), so I expect that embedding them in the cocoon is a useful defensive measure to keep the pupa inside from getting eaten.

And then, about a month later (June 15), a large, nearly black moth with an orange neck emerged – a Ctenucha virginica, exactly as I predicted!

I think this picture set better shows the iridescent blue coloration of the body than the previous one. Also, the 2007 specimen had much more feathery antennae, so that one was most likely male and this one is almost certainly female.

I let it go by letting it fly out the window, and it ended up perching on the outside for a bit, allowing a chance for a few pictures of the underside.

We can actually see the curled up proboscis here, including the tip. It looks like it can stick out part of the proboscis for a quick drink without having to unroll the whole thing, which could be quite a timesaver. And, in fact, if you look back at the earlier photographs of this moth, in some of them you can see the proboscis tip projecting out of its face, pointing a bit to the side.


Anyway, these are a variety of tiger moth, and like most tiger moths their fuzzy caterpillars hibernate through the winter as caterpillars. Then in the spring, they pupate and emerge as adults in early summer, at which point they lay their eggs. The caterpillars are opportunistic feeders that mostly eat grass, so they don’t get seen too much unless one starts running a sweep net through an overgrown lawn. The caterpillars are most obvious in the spring when they crawl out looking for places to make a cocoon.

The moths are believed to be mimicking wasps with their iridescent blue body color. They do look a little bit like a number of solitary wasps, like the similarly-sized blue mud dauber, although the mimicry is not all that convincing. Still, it may be good enough to convince a bird, spotting it from some distance, to not follow up and investigate further. Then again, they may just be mimicking the many other local insects that use orange and black to advertise their foul taste. And, it is even possible that they taste foul themselves, further boosting the reputation of that particular color combination amongst predators. Whatever they are doing, it must work reasonably well, seeing as how these moths are pretty common locally.

8 Responses
  1. April 18, 2012

    Where does the silk come from? Does it get extruded through body pores?

  2. April 18, 2012

    Pretty much all caterpillars have silk spinnerettes on their lower lip. To spin a cocoon, they weave their head around and periodically flip over to get at both ends. They usually seem to do it at night, so I haven’t actually caught one in the act of cocooning up yet. Other people have, though: here’s a video of a silkworm doing it: http://youtu.be/ChBpihQRlaU

    It looks like a lot of work.

  3. JennyW permalink
    April 18, 2012

    beautiful! I love the body colors.

  4. April 19, 2012

    Aha! The cocoon isn’t as tight as it looks! Thanks for sharing that video. Great stuff!

  5. May 24, 2012

    Thank you so much for this amazing site! I’ve just discovered your blog and love it! My kids found a Ctenucha caterpillar yesterday and it spun its cocoon last night. They are fascinated by it! I wrote a post on it (http://mommaowlslab.blogspot.com/2012/05/from-caterpillar-to-moth-ctenucha.html) and referred back to your great site!

  6. May 25, 2012

    Thanks, Rachel. I like the way that you photographed your cocoon with back-lighting, so we could see the caterpillar spinning it inside.

  7. July 8, 2015

    Have honeybees and these moths come and scoop up a bee and fly away with them. Is this common behavior? Any info?

  8. July 8, 2015

    Ed: No, that is not normal behavior for a moth. But, there are wasps that hunt bees, and these moths do resemble certain wasps.

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