Poison Ivy Caterpillar / Dimorphic Macalla Moth

May 20th, 2012 - 4:36 PM | Filed under Featured Photos | 3 Comments

For many years I’ve noticed colorful little caterpillars that live individually in silken retreats on the surface of leaves of poison ivy. At a recent BugGuide gathering, a photo of one of these caterpillars was shown and I realized we still didn’t know what these were. I resolved then to rear a few to try and arrive at an identification. There’s plenty of poison ivy near my home, so I didn’t anticipate much trouble finding a few.

Here’s the first one I found. The white area just behind the head is atypical. The caterpillar is smaller than usual, so it might be an early instar. It could also represent some sort of injury.

13mm | August 20, 2011 | Roswell, GA, USA

The next day I collected another one, larger.

20mm | August 21, 2011 | Roswell, GA, USA

The next weekend I collected one more.

20mm | August 27, 2011 | Roswell, GA, USA

Here’s a cropped version of the image above, showing the head. Checking these specimens and other photos on BugGuide, there appears to be quite a bit of variability in the head coloration. They all have a white band across the lower part of the head capsule though.

Closeup of head

At that point I figured I had a good chance of successfully rearing at least one.

The last one I collected was the first to pupate. A few days before pupating it started to change color. That’s not unusual for caterpillars as they prepare to pupate. In this case it darkened to become more orange.

Prepupal stage of final instar | 9 September 2011

Another closeup of head

I neglected to photograph any of the pupae.

Earlier this month, an adult eclosed. It’s attractive and quite distinguished looking with an elaborate headdress.

20mm wingspan | 4 May 2012

Lateral view

Front view

Closeup of head

After searching through various guides, I decided this must be what’s currently known as Macalla superatalis. My books actually identified it as part of a genus it was previously placed in, Epipaschia. The common name, Dimorphic Macalla (previously Dimorphic Epipaschia), refers to the fact that it comes in two color forms: green as above, or tan.

Having arrived at the identification, I checked BugGuide and found that someone had beat me to the identification based on a literature search. Oh well, it looks like I might be the first there to have successfully reared them though.

References:

A Field Guide to Moths of Eastern North America
by Charles V. Covell, Jr.
Peterson Field Guide to Moths of Northeastern North America
by David Beadle and Seabrooke Leckie

3 Responses to “Poison Ivy Caterpillar / Dimorphic Macalla Moth”

  1. Nice job – both with the rearing and with the photographs.

    It would appear the headdress are the palps extending up and over the head?

    • Troy Bartlett says:

      Thanks, Ted. I assume those are the palps. I’m not sure what else they could be. I’ve seen moths with palps sticking up or forwards, but this is the first time I’ve seen them curling up and over to that extent. Makes for a nice effect!

  2. Great shots! I especially like the lateral view.

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