Ogre eyes

When I go out into the rainforest at night, I bring two flashlights. I don’t wanna be out there without light. The dark is imposing. My flashlight provides me with a little shelter from the dark, a small bubble of visibility. But I know that if my battery goes out—if the bubble bursts—the night will flood in upon me. It’s better to just bring a spare.

            It’s kinda cool in my little bubble though. My perception is limited because I can’t see past the film of the night. The only thing I can see is what my light touches: a branch, a fern, a palm leaf. So there’s no question about where to look. I don’t have a choice—wherever my light lands.

With my perception channeled into one point, I look more closely at whatever is illuminated. I move more slowly and find things I previously might have missed: a cat-eyed snake ascending a vine, the eye-shine of a wandering spider on a bromeliad, a cask-headed lizard pretending not to exist. It’s a different world in the rainforest at night, and a flashlight is my visa.

The weird thing is that I tend to forget the rainforest isn’t actually illuminated. Since I can’t see it without a beam of light, I can’t form an accurate image of what the rainforest looks like at night. So I turned off my light. The world disappeared.

Only for a second though. Then sounds started to emerge—a chorus of drones and groans and cheeps and chirps. Each sound was a reminder that though my world had disappeared, life here was very much still happening. Loudly.

I looked to my left—nothing. I looked to my right—nothing. I waved my hand in front of my face—still nothing. I waited. I wanted to see how long I could last without my headlamp on. Turns out over a minute was too tall an order. 

When I turned my headlamp back on, my light was shining directly on a net-casting, ogre-faced spider. Its twig-thin body hung motionless above a mossy palm leaf. My light beam reflected off its translucent blue silk-snare, stretched out between its forelegs like the string of Jacob’s ladder. It was ready to strike, to drop down and pluck up an unsuspecting insect in the blink of an eye.

I was startled by how unfazed the spider was by my light. It didn’t even twitch. It could catch its prey perfectly fine in conditions that left me incapacitated.

Ogre-faced spiders have a pair of greatly enlarged eyes that consist of an array of compound lenses. This enables their eyes to refract light almost twice as efficiently as an owl. They don’t even have a permanent retina. Instead, they construct a fresh photo-sensitive membrane. This grants them a brand new set of eyes every night.

Other spiders have a different adaptation. Cupiennius spiders have finely tuned hairs on their bodies that are capable of detecting the slightest disturbances in the air.  A passing cricket churns up the air enough to garner the spider’s attention. 

The 45 seconds I spent with my light off reminded me just how limited my senses are. It’s one thing to read about the extraordinary adaptations in nature. It’s quite another to be alone in the dark of the rainforest and compare them to your own.

Tom Jackson

University of Virginia