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Saddleback Caterpillar

saddleback caterpillar
Saddleback caterpillar, Acharia stimulea (Lepidoptera: Limacodidae) (Photo: Dr. Art Evans)

Entomologist Dr. Art Evans and VPM radio producer Steve Clark discuss a common and venomous insect that is widespread in eastern United States, the saddleback caterpillar.

Steve Clark:  I'm Steve Clark with Dr. Art Evans, entomologist, and this is What’s Bugging You.  

 Art Evans:  We just had our lecture in medical and veterinary entomology the other day on stinging insects. 

Clark:  Oh, one of my favorite categories. 

Evans:  So when you think of stinging insects, what do you think of?

Clark:  Well, I think of bees and wasps.

Evans:  Well, did you know that some caterpillars sting too?

Clark:  No.

Evans:  Yeah, some caterpillars are covered with spines, spines that are hollow and associated with venom glands.  I mean, they are capable of delivering toxin to your person.  One of the more well-known venomous caterpillars in eastern North America is the saddleback caterpillar. You ever tangle with one of those?

Clark:  No, I don't know that I've ever seen one in real life.

Evans:  They're a very attractive caterpillar, which is deceptive.  But it is an aposematic color pattern.  They have bold brown and green and tan markings that sort of suggest caution is in order.

Clark:  But there's a saddle. 

Evans:  There is a saddle.

Clark:  And no stirrups. 

Clark:  No stirrups, hence the name saddleback caterpillar.  That's absolutely true.  The first experience I had with a saddleback was indirectly.  I had just moved to Richmond, and there's a knock on my door.  And it's one of my neighbors, and she said, “I hear you're an entomologist.”  [laughing] And I always laugh at that, you know, because well, I'm one of many.  And she said, “Well, is this going to get any worse?”  And she was wearing shorts, and on the inside of her thigh, she had the silhouette of a saddleback caterpillar.  She had walked right into one.  And they have a tendency to feed underneath leaves.  So people working in their gardens will brush up against them with their forearms, or their legs, not even realizing they're there.  And they will light you up.  

Clark:  But she had the image of it?

Evans:  I could make it out.  I recognized what it was.  You could see all the points where the spines hit her.

Clark:  Oh, I see.

Evans:  And it vaguely looked like the imprint of this caterpillar.  [laughing] And for years I’ve recounted that story, you know, sort of a second-hand version of what I know about caterpillars.  Well, the very day before class in the fall, one of my neighbors brought over a cookie tub full of these caterpillars, and I thought, “Fantastic, I've got show-and-tell.”  Five minutes before the start of class, the first introductory lecture, you know, introducing everyone.  And I thought, “Well, I'll just add a fresh leaf or three to the tub.”  And one of the caterpillars was just right up on the edge of the container, and I reached over, and I inadvertently jerked, and I rubbed my knuckle across the caterpillar and boy, did it hurt. [laughing] And all through the lecture I was very uncomfortable, and I just had to come clean with my students right away, saying, “If I seem distracted, it's because I am.” [laughing] They are covered with an array of these venomous spines, and the spines can break off in the skin, and they deliver venom that breaks down tissues.  It can cause blistering; it can cause bleeding.  They belong to a group of caterpillars called slug caterpillars.  They have glands on the underside of their body, and they secrete a slime, and instead of having little hooks on their prolegs or their padded feet, they have like suction cups, and they sort of glide over a slimy trail.

Clark:  Slithering along.

Evan:  Yeah, and they're very slow.  They are what we call in the biz, polyphagous.   They eat everything.  They are not particular at all.  You'll find them on all kinds of plants. 

Clark:  Dr. Art Evans is a research associate at the Virginia Museum of Natural History.  You’ll find photos and audio, links to the museum and Art’s Facebook page at

Dr. Arthur V. Evans teams up with VPM Radio producer Steve Clark for a weekly feature, “What’s Bugging You?,” which airs during NPR’s Morning Edition. The program takes its name from another of Evans’ books “What’s Bugging You – A Fond Look at the Animals We Love to Hate.”

Tune in each Tuesday at 8:45 a.m. or at 5:44 p.m. on VPM News