Appalachian Field Note · AIG-000011

Witches’ buttercf. Tremella mesenterica

After the rain, the log was dotted with yellow jelly. I photographed it, and a millipede walked through the frame as if I were not there.

July 25, 2026
Exercise Trail #344
Pisgah National Forest
Natural notes by Will Thomas

Natural note

The yellow looked almost painted on

Against soaked brown wood it was too bright. Small jelly bodies were coming out of fissure after fissure, some no larger than a bead, others folded into translucent cups. The photographs make the fungus look like it is glowing. It is wet tissue, warm light, and a yellow pigment.

What looks like a fungus eating a log is a more complicated scene. Witches’ butter is best understood as a mycoparasite. Its likely target is a crust fungus in the genus Peniophora, mostly hidden in the wood. One fungus occupies the branch. Then another fungus taps into it. Downstream on the same trail, a bolete mold shows a different fungus-on-fungus story.

Its actual occupation

The log is the stage, not the meal

Peniophora fungi live as thin crusts or hidden mycelium on dead wood. Tremella mesenterica inserts specialized feeding structures into that fungal host and takes resources from it.

That makes this a small food web with no leaves and no chase: wood, a crust fungus, and a second fungus exploiting the first. The gold you see is the spore-producing phase of that relationship.

Why this comparison fits

What I can see, and what I cannot

Golden and gelatinous

The fruiting bodies are saturated yellow, smooth, glossy, and translucent at the edges. They hold irregular folds. There is no cap, stem, pore layer, or gill.

Many points on wet wood

Buttons and larger lobes emerge across decorticated fallen wood after rain. That is how a jelly fungus usually looks when it has taken on water.

No Stereum brackets visible

The close lookalike Naematelia aurantia is tied to Stereum. None of those bracket-like host fruiting bodies appears in these frames.

What the camera did not settle. The tree species and the expected Peniophora host were not documented. Dacrymyces chrysospermus can look similar and is usually associated with conifer wood. No spores or microscopic structures were examined. For that reason, the formal record stays at cf. Tremella mesenterica.

Photography sequence

Gold in the grain

Overhead view of bright yellow witches' butter fruiting bodies, some small buttons and some folded lobes, emerging from cracks in rain-soaked decorticated hardwood — 01Small buttons and folded lobes follow cracks in the wet log.

02A close profile shows how much water the lobe is holding.

Wide view of a witches' butter colony: many separate yellow jelly fruiting points on layered wet fallen wood after rain — 03The colony is not one continuous mass. Fruiting points are scattered across the log.

Low-angle view across rounded yellow witches' butter lobes on rain-darkened fallen wood in filtered afternoon light — 04From this angle the lobes sit like small cups of water and pigment.

Who is eating whom

A 12-inch neighborhood on wet wood

Photographed 12-inch neighborhood: yellow witches' butter jelly scattered across layered wet wood with moss in the cracks — The photographed neighborhood is about a foot across: wet wood, moss in the cracks, yellow jelly, and later a millipede.

01 · Substrate Dead hardwood Rain-darkened, bark already gone in places. The wood holds water and gives the first fungus somewhere to live. I did not identify the tree.
02 · Hidden host Peniophora, usually unseen A crust fungus that actually uses the wood. It may be only mycelium in this log. I did not find a visible crust in these frames.
03 · The feeding tool A microscopic pore Tremella sends a fine filament into a host cell. At the contact point, a single micropore connects their cytoplasm. That is how the gold jelly feeds.
04 · What you notice Yellow jelly The public part. After rain it swells and shines. Dry, the same tissue shrinks toward a thin crust. It is not eating the log.

One weird thing

It feeds through a pore between fungal cells

A 1994 microscopy study documented specialized haustorial cells in Tremella mesenterica. Fine filaments penetrate the wall of the host fungus. At the contact point, a single micropore connects their cytoplasm.

The gold jelly is the public part. The feeding happens cell to cell, out of sight. I did not see that pore. The literature describes it.

Host

A crust fungus in the genus Peniophora, usually hidden or visually modest on the wood.

Tool

A tremelloid haustorial cell with a narrow penetrating filament.

Result

Resources move from one fungus to another, while the yellow fruiting body produces and releases spores.

Dark flat-backed millipede, compared with Oxidus gracilis, walking on wet wood beside a large golden witches' butter lobe. The photograph shows proximity, not feeding. — A flat-backed millipede shares the log. The photograph records proximity, not feeding.

Who else showed up

A millipede used the same log

The dark, glossy animal is consistent with a small flat-backed millipede, cf. Oxidus gracilis. Pale legs and lateral flanges show in the linked sequence.

Nothing in the frame proves it was eating the fungus. It may have been grazing on decayed plant matter or microorganisms elsewhere on the log, or simply passing through. The honest story is co-occurrence. The flat-backed millipede field note covers that animal on the same log.

Colors sampled from the photographs

Gold, wet cedar, moss, and millipede ink

Rain-Lantern Goldsunlit jelly lobe#FFCC0E

Trembling Amberfolded fruiting body#F6B300

Wet Cedar Platedecorticated log#624A32

Moss in Shadowmoss-lined wood#36311E

Millipede Inkflat-backed millipede#120B01

Each hexadecimal value comes from one recorded pixel in the Rogue7 sequence. These are image colors, not calibrated measurements of the fungus. Flash, white balance, wet surfaces, and surrounding wood all influence the result.

Names and people

Where the name comes from

Trembling, and a membrane

Tremella points to trembling. Mesenterica compares the folds with the mesentery, the membrane that supports the intestines. The common name belongs to older European stories that treated strange yellow jelly near a house as witchcraft, material left by a familiar, or evidence of a spell.

Foraging, kept in its place

Witches’ butter shows up in edible-mushroom traditions and modern foraging talk, often valued more for texture and color than for flavor. This field note is not an identification or preparation guide. I did not taste it. If the human relationship interests you, start with habitat care and local land rules.

Forest Service picking ethics NAMA stewardship

Keep walking the same trail

Other Davidson River field notes

Same log Flat-backed millipede The animal that walked through this frame, treated as its own record. Fungus on fungus Bolete mold Another parasite using a fruiting body as its address. Wood decay Chicken of the Woods A brown-rot bracket working through a different wet log. Same trail Shaggy-stalked bolete An ectomycorrhizal bolete from Exercise Trail 344 on the same wet July day. Same forest Carmine-pored bolete A red-pored bolete in the ferns, still a photographic comparison. Same forest Ornate-stalked bolete A heavier reticulate stalk from the same Davidson River woods.

Field record

Davidson River, after rain

Observation: AIG-000011
Date: July 25, 2026
Time: 1:51 p.m. to 2:27 p.m.
Location: Exercise Trail #344 near Davidson River Campground, Pisgah National Forest
Coordinates: 35.28275, −82.7242667
Elevation: 663.4 m
Disposition: Photographed in place and left undisturbed

References