Silk Crossing

The katydid crept cautiously.

She was scaling our home’s vinyl siding. Slowly and deliberately, she would lift a leg. Sometimes, she waved it in the air. Then her foot patted the siding several times before committing to a landing spot. She seemed to be checking for obstacles like a sight-impaired person might use a cane to survey the sidewalk.

I peered closer. Then I saw the reason for her wary walking.

Taut silk threads crossed her path like fence wire, nearly invisible against the siding. They ran in long horizontal rows, the work of a spider that was probably hiding beneath one of the vinyl panels.

Despite her long legs, the katydid didn’t seem inclined to climb over the fence. She pushed through it, seemingly nonplussed when she tangled with the silk.

Watch as she crosses two silk lines.

Did you see the silk in her mouth? At first, I thought she was eating it. Then I realized she was chewing through the lines, using her palps to hold them for cutting. The palps are those four finger-like appendages around her mouth, and you can see they’re quite nimble. They’re sensitive too, in the truest sense of the word. Katydids (and cousins including grasshoppers, roaches, and crickets) use these sensory organs to taste food.

Here’s another clip that gives a better view of her vertical navigation.

The videos play in real time—she’s moving in what seems to be slow-motion.

The biggest question I have after watching the katydid scale the siding: Why? They’re primarily leaf-eaters, consuming the occasional dead insect or insect egg. Was she shopping for carrion caught in the spider silk? This side of our house is just five feet from the woods’ edge. I took the video in October, when there was plenty of green vegetation available for a katydid’s dinner. I used an iPhone with a clip-on macro lens that requires me to be within an inch of my subject. The katydid seemed unperturbed by my nosy peeping… until I got too close. She bailed, gliding on her broad wings to the adjacent vegetation.

A few minutes later, she returned to the house and climbed up a door. A friend told me that growing up, she found katydids on her home’s siding quite frequently. So, I’m puzzled: What’s the attraction?

And… how does an insect adapted to climb vegetation get a grip on a shiny surface? The siding has texture, but the door is untextured and glossy. I’m familiar with how geckos scale shiny vertical surfaces, even glass, with toe hairs that use molecular, opposites-attract bonding forces. So, I wondered if the katydid had similar equipment.

I sent that question to a marvelous group of entomologists who answer such queries on their website, Ask an Entomologist. One of the team emailed me the answer: ‘The first thing that insects have going for them is that they’re relatively small and light. That helps them stick onto smoother surfaces. Many insects, katydids included, have tarsal claws which help them grip onto small imperfections in smooth surfaces. In addition – katydids along with grasshoppers and crickets, have little pads on their feet that also help with adhesion.’

So, now I know how the katydid climbed the side of my house. But Google as I might, I found no reason why. If you have any theories, I’m all ears. And oh—about those katydid ears. Something else I learned while meandering through the katydid literature: Her ears are on her legs. You can see them in the first video: small, brownish ovals on her front legs just beneath her knee joints.

She waved those legs at me. I’m sure she had no trouble hearing me ask, ‘are you lost?’

I linked to some of my sources above. Here are a few more:

Katydids (University of Wisconsin Extension)

Katydid song (Songs of Insects)

Katydid song (Lisa Rainsong’s wonderful blog)

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