Wednesday, April 19, 2006

Here's what may emerge from Brad's pupa

Abbott's Sphinx Moth - Sphecodina abbottii
Photo by Janice Stiefel
Fish Creek, Town of Gibraltar, Door County, Wisconsin, USA
April 25, 2003
Adult eclosed from overwintering pupa.

From a website correspondent:

Hi Marie:

What's happening with the cocoon you were keeping an eye on for so long?
I am not sure if I missed the lastest posting regarding that on your website or not.
It has been on my mind and would love to know.

Shelly Lane

Dear Shelly,

I'm not sure which one of our potential lepidopterans you're thinking of. If you're wondering about the little "cocoon" in Shakespeare Garden, that one is still there, looking exactly the same as it did last fall.

Black Swallowtail chrysalis after metamorphosis - 10/6/05
Photo by Lloyd Spitalnik

It's actually a chrysalis or pupa, not a cocoon, the cocoon being a silky case many butterflies and some moths spin to enclose the pupa. We're keeping an eye on it to see if there are any changes that might indicate an emergence about to happen. In fact I just checked it this afternoon [4/18/06]. Looked just like it looked in the photo above. We know that a Black Swallowtail Butterfly is going to emerge from that chrysalis because we identified the caterpillar in a wonderful new field guide, Caterpillars of Eastern North America by David Wagner.

Black Swallowtail Caterpillar attached to slat -- 10/5/05
Photo by Lloyd Spitalnik

We watched the caterpillar wander around on the fence looking for the right spot. Then we saw him attach himself by two silky threads to a fence slat, shed his skin and metamorphose into the dried gray pupa you see on the second photo above. If you look carefully at both the Black Swallowtail photos you can see the two attaching threads quite clearly.

But maybe you're thinking of the big pupa found last fall -- see picture below. That one's actually not a cocoon either. Brad Klein, a Vice President at Acoustiguide and a Central Park Naturenik, found it,
photographed it, and named it Squirmy for its behavior when it's picked up.

Squirmy, a large pupa found in Central Park on 10/14/05
Photo by Brad Klein

I paid a visit to Squirmy last week. He is still on his sphagnum moss bed in a well-aired jar in Brad Klein's refrigerator. That's where Squirmy spent the winter, following the instructions of various people who have successfully reared moths from pupae.
We're pretty sure he's a he, having "sexed" him according to instructions found in a book called Rearing Moths. . Brad gently mists him every week to keep him from getting dessicated. He'll be placed out on Brad's terrace any day now in hope that he'll eclose --the entomologists' term for turning into a moth or butterfly.

We know he's a moth but aren't sure what kind. The most likely family is the Sphinx Moth family. The most likely species is The Abbott's Sphinx [Sphecodina abbottii], though it has never been seen in Central Park.

David Wagner has this to say about Sphinx Moths:

“Sphingids possess the most acute color vision of any animals, discriminating floral colors at light intensities that would appear pitch black to the human eye.”

Wagner has more to say about the Abbott’s Sphinx caterpillar, the very species Squirmy may prove to be. In the last stage of the Abbott caterpillar's development, an orange horn on its eighth abdominal segment is replaced by a convincing false eye that closely resembles a vertebrate eye with a black central pupil and encircling iris. Wagner continues:

"Added deception is provided by a 'white reflection spot' that makes the eye appear moist and shiny. If the 'eye' is poked or pinched, the caterpillar squeaks, reels around and bites its attacker."

Abbott's Sphinx caterpillar with deceptive "eye" [a dot of white pigment]
From BugGuide

Just for comparison, here is a bird with a real white reflection spot:
Brown-headed Cowbird in Central Park - 4/12/06
Photo by Lloyd Spitalnik

Anyhow, thanks for writing, Shelly. I'm so glad someone's interested!