Saturday’s big gardening adventure came in the form of a venomous spine lodged in my leg. Ouch!

The culprit — a saddleback caterpillar — was munching on a kale plant. I didn’t even see him. I just stepped away from tending a tomato plant, and backed my leg into the caterpillar’s chosen kale leaf. Fast forward .0042 seconds, and I’m leaping into the air wondering what creature of hell had just attacked me. Based on the suddenness of the pain, I expected my assailant was a yellow jacket, hornet, or baby Velociraptor. I didn’t suspect a caterpillar. Especially not a 1-inch caterpillar.

But that’s exactly what happened. A close inspection of the kale plant I’d backed into revealed a mess of caterpillar damage, a bunch of run-of-the-mill cabbage worms, and a prickly little beast that I vaguely recognized from my trusty Audubon Society insect guide. I knew I’d found my attacker. The little thing was just loaded with short spines. Here’s a photo of him on my poor, half-consumed kale plant. Yes, that’s a head shot:

And, here’s another photo of the beast, taken after I’d very very very carefully removed him from the kale plant:

Prickly! Beware: Every one of those spines is loaded with hemolytic (blood-destroying) and vesicating (blister-creating) venom, and they will readily jab you whether you see the caterpillar or not. Long pants, long sleeves and gloves may offer some protection, but not complete protection — I was jabbed right through the denim of my jeans.

In North America, only the puss caterpillars of the moth family Megalopygidae are more venomous than the saddleback caterpillar.

Here’s how the University of Florida’s entomology guide (the best I found) describes the saddleback’s effects:

The spines of A. stimulea are strong, acutely pointed, and hollow. They embed deeply into tissue and break off, and can interrupt healing as the protoplasm from the venom glands dries into the tissue area. … The venom itself can cause a systemic condition called erucism or acute urticaria, for which severe symptoms may include migraines, gastrointestinal symptoms, asthma complications, anaphylactic shock, rupturing of erythrocytes, and hemorrhaging…

Sounds nice, right?

Reading this, I know I got lucky. No nausea. No migraines. No shock. Not even a rash. Just an immediate burst of super-intense pain that lasted until I removed that venomous spine (only one made it past my jeans) and numbed the area with a cube of ice. Very lucky. I think I escaped the worst of it because I was wearing jeans, which surely offered some protection (though clearly not enough). Also, I found and removed the single spine within a minute of getting jabbed. I was highly motivated — the tiny little spine HURT.

Still, I find it mind-boggling that an inch-long caterpillar can cause that list of symptoms. After a bit of searching around the internets, I found bunches of stories about much worse encounters with these nasty little guys. Some people even wind up in the emergency room. There’s a good collection of folks’ saddleback caterpillar stories here.

After a weekend of compulsive reading, I can offer the following information about these prickly caterpillars:

Full name: Saddleback caterpillar or saddleback caterpillar moth

Scientific name: Acharia stimulea (formerly Sibine stimule)

Range: The eastern half of the United States, from Massachusetts to Wisconsin and south to Florida and east Texas.

Diet: Saddleback caterpillars can feed on a variety of plants. The one that got me was on a kale plant, but reports also indicate they feed on deciduous trees and shrubs, vegetables, flowers, and just about anything.

Life cycle: The timing of this varies by region, of course. Adults appear to emerge at the onset of consistently warm weather (June/July in the far north of their range, February/March in the most southerly part of their range). Females lay clusters of 30-50 eggs, and the larvae hatch in about ten days. The caterpillars hatch and feed in a group until they’ve molted once or twice. Then, they disperse (not sure how far). It appears to take approximately four months for these caterpillars to reach full size, which explains why most interactions between saddleback caterpillars and people appear to happen in the late-summer months; that’s when the caterpillars are larger and more likely to be encountered.

Note: Saddleback caterpillars develop their venomous spines after their first molt, which means that even very small saddleback caterpillars can sting.

How to avoid being stung: I’ll give you the bad news first. You can’t totally eliminate the possibility of a saddleback caterpillar attack. Well, that’s not entirely true. If you live in the eastern half of the United States, you could pack everything up and move west (where these caterpillars are not found). Up to you if you want to take things that far.

Otherwise, it’s just a matter of reducing risk:

• Wear long pants, long sleeves and gloves, especially in the late-summer months (yes, when it’s stinkin’ hot). I’m positive I got off easy because I was wearing jeans rather than shorts.
• Learn to recognize saddleback caterpillars.
• Be cautious when handling or walking past/through vegetation that shows obvious signs of caterpillar damage.
• If you find one, chances are good there will be more nearby. Carefully look over the host plant and neighboring plants. Be careful — you don’t want to feel the caterpillars before you see them. It may be wise to carefully remove the entire host plant (depending upon the plant, of course).
• Relocate or kill any saddleback caterpillars you find. Do whichever you think is best. But, bear in mind that one venomous caterpillar this year could turn into 30-50 venomous caterpillars next year…

However you deal with saddleback caterpillars, keeps this bit of information in mind:

Spines of urticating caterpillars can become airborne and consequently be inhaled or contact sensitive tissues like the eyes and nose. They may also embed in surfaces such as wooden tables and plastics, which become a contact hazard at a later time if the area is not cleaned. Stray spines can also get caught in fabrics, such as carpet, aprons and clothing and come into skin contact that way…

In other words: Be careful.

For even more information about saddleback caterpillars, including some fantastic photographs of the adult moths and young larvae, check out the species summary provided by the University of Florida’s entomology department: Saddleback caterpillars (Acharia stimulea).

Are you familiar with saddleback caterpillars or other unfriendly caterpillars? Any more tips to share that I may have missed? Please click here to add you advice in the comments section below.