Not waiting for comment, she kept walking. We stepped into an opening where a mammoth tree had fallen, taking down half a dozen other behemoths with it. They lay broken across one another in different stages of decay, carpets of verdigris moss melting over hills and valleys of bark and branch. Hundreds of purple butterflies burst from a rotted trunk as we passed, swirling in a violet funnel over our heads. A yards-long spiderweb that draped like lace from branch to branch above us was clotted with the purple wings; a fist-sized spider huddled in a dark corner, waiting.

“I never capture the butterflies, because then the spirit leaves them.” She stepped over a few logs, stopping at one as tall on its side as she was standing. Big black ants swarmed a rubber tree sapling that had sprouted up through the rotting log, exposing a V where an abandoned bees’ nest still glistened with honey. “But when I see them, I know I’m near my nest of bullet ants. The isula. You know this ant?”

I shook my head. I’d never heard of it, but knew that—in this place—if an insect had a name, it was best to stay away from it.

“The bite of this ant is like a bullet. For a whole day, your enemy will be in terrible pain.”

She took out a short bamboo tube, flipping the rubber cap free with her tobacco-stained thumb. With a stick, she dabbed honey in the bottom, then lay the tube next to the ants. Dozens crawled in before she kicked the container a short distance away, rolled it under her sandaled foot—crushing the ants that remained on the outside—before snatching it up, snapping the rubber stopper back on, and slipping the tube in her string bag.

“Come on.” She led me past the graveyard of fallen giants to one that stood tall, its roots like flying buttresses soaring up and out of sight, its base as wide as a city bus. “This is the lupuna tree. They are sacred. One must never relieve oneself near here. This is where I can hide my soul and keep it safe if some brujo or bruja is coming after me. Now, look closely here, in these plants that grow near the roots. This is where the poison frogs like to live. See?”

Four jewel-toned orange-and-blue-spotted frogs, each as big as a thumb, hid in bright green nests, bulbous toes gripping the leaves. Black eyes watched our approach; each blink revealing brilliant yellow eyelids. Throat sacs pulsed, skin glistened.

“This one makes poison through the skin, do you see it? How it is shining like that? This one makes enough poison to kill ten men, fifteen men. We use these frogs for arrows, and for darts for the blowguns, to kill. Or we can use a little to make pain go away, to numb. A drop under the skin makes a baby sleep for hours. Four will kill it.”

She reached in her string bag and pulled out a small, woven palm box. A frog’s little fingers scrabbled at the slits between the fronds. “See? Very useful.” She straightened up with a groan. “Do you have these frogs in Boston?”