Tortoise beetle larvae protect themselves from predators by
creating a shield of ‘distasteful’ items collected on forked
structures at the tip of the abdomen.
July 18, 2014
Tortoise Beetle
Thar’s gold in them thar hills!
But hold on a sec. Before you run for your pans and pick axes, we should probably clarify a couple
things. One, the hills in question are located in the Hickory Knolls Natural Area, where no digging is
allowed. And two, the gold isn’t the precious-metal type, though it is indeed a treasure – especially if
you like bugs.
What we’re talking about this week are golden tortoise beetles, Charidotella sexpunctata. As we have in
summers past, we once again have discovered these little gems–a fairly common species in our area–
hanging out on bindweed, one of the insect’s favored food plants.
Thanks to some built-up fluids and a really neat optical illusion, these beetles look for all the world like
drops of gold glistening in the sun.
As I stood there admiring their beauty, I realized that, once again, I was going to miss out on an
opportunity to snap a photo of these truly glorious creatures. I did have my phone with me, but its
ability to capture tiny things like tortoise beetles (which are about ¼-in. in length) combined with my
own limited photography skills, meant a mental picture was as good as it was going to get.
I consoled myself by giving the beetles a couple of light pokes.
I know, it sounds bad, as if I were taking out my
disappointment on some poor defenseless
arthropods. But my intent was not to harm them;
rather, I just wanted to see the beetles change color.
And, did they! In a flash they transformed from rich
metallic gold to a still-shiny, but much less impressive
reddish-orange.
Researchers are divided on the purpose behind this
behavior. Does it confuse predators? Is it an attempt
to mimic ladybugs, which use chemical deterrents to
avoid getting eaten?
While the reasons may be murky, the science of how it occurs is not.
The beetle’s normal – or “at rest” – golden hue is created when light reflects off liquid that is held in thin
grooves between the layers of the insect’s transparent elytra, or wing covers. But when the beetle is
agitated or stressed, it drains the moisture away, revealing an underlying color of ladybug-red, spots
optional. The color change also can occur during periods of extreme drought, when the insect might not
have an adequate moisture intake, as well as when the insect dies.
Being able to change color is a cool trick, as anyone who’s ever observed it can attest. But this species
displays an even more interesting behavior that has no doubt saved the lives of many young beetles
over the ages.
As larvae, tortoise beetles are dark in color, with soft, fringed spines along their sides and a two-pronged
“anal fork” at the rear of their abdomen. Quite a bit of ornamentation for a young insect no bigger than
a collar button. But it gets better.
That forked appendage is good for more than just looks. It’s also a collection device.
You’re probably wondering what, pray tell, might a beetle larva need to collect? The answer is twofold:
shed skin and fecal matter.
So now you’re probably wondering… why?
Shed skins and fecal matter, as you might imagine, are distasteful, and generally are regarded as items
to avoid. But if you happen to be a helpless beetle larvae, jam-packed with nutrients other creatures
might find useful, distasteful is exactly what you want to be.
Over time the shed skin and droppings build up on the fork, arching over the young beetle like an
umbrella – a poop parasol, if you will. In theory, it’s a great defense against predators.
But no defense is perfect. (If it were, we’d be overrun with tortoise beetles!)
For example, members of the insect order Hemiptera, the true bugs, are equipped with piercing/sucking
mouthparts. Picture a dinky, hinged drinking straw permanently attached to a bug’s head and you’ll
start to get the idea. While many species use their straws to feed on plant juices, others plunge their
predatory probes into animal food sources — such as tortoise beetle larvae.
Piercing, sucking predators notwithstanding, tortoise beetles are still pretty easy to find.
Golden tortoise beetles and their handsome cousins, the mottled tortoise beetles, have a taste for
plants in the morning glory family; the clavate tortoise beetle, my personal favorite, hangs out on plants
in the tomato family, namely ground cherries, jimsonweed, horse nettle and nightshades. (Why pick one
tortoise beetle over another? In a word, charm. The clavate species has spots on its back in the shape of
— I swear I’m not making this up — a teddy bear. Talk about being cute as a bug!)
The next time you find yourself shaking your head at the invasive bindweed entwined on your
perennials or the nightshade under your shrubs, take a minute to check them over. You might find you
have a tiny drop of gold, or even a teddy bear, perched on them thar plants.
Pam Erickson Otto is the manager of nature programs and interpretive services at the Hickory Knolls
Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-639-7960 or