the pitted crust lichen etched into NZ's smooth bark
- Size
- Width: 2–8 cm
- Lifespan
- 10–50 years
- Diet
- Grows on bark of trees, rocks, and wood in damp, shaded forests. Requires clean air, stable bark surfaces, and high humidity. Forms crustose thallus with distinctive, pore-like fruiting bodies (thelotremoid apothecia).
- Habitat
- Grows on bark of trees, rocks, and wood in damp, shaded forests. Found in moist, sheltered locations where the bark is rough and the air is humid.
- Range
- Found throughout the North and South Islands on bark of trees, rocks, and wood in damp, shaded forests. Most common in the South Island's beech forests and the North Island's western ranges. Also found in temperate regions worldwide.
- Endemism
- Native
- Main Threats
- None significant. This species is common and widespread in damp, shaded forests. Localised threats include forest clearance, air pollution, and climate change reducing forest floor humidity.
- Population
- Not Threatened. Thelotrema lichen is common in damp, shaded forests throughout New Zealand, particularly on the bark of native trees in undisturbed locations. It is easily overlooked due to its small size, but it is widespread.
- Conservation Status
- Not Threatened
The one that looks like it is watching you has a body that is a thin, crusty layer that grows on the surface of the bark, forming a pale greyish-white to off-white patch. The crust is smooth and even, like a coat of pale paint. But scattered across the surface are tiny, delicate openings, the fruiting bodies (apothecia), that look like miniature eyes. Each opening is ringed with a raised, pale rim, and the centre is dark, like a pupil. It is the lichen of the watching eye, the one that seems to stare back at you from the bark.
What makes it special is the eyes. Thelotrema lichen is one of the most distinctive lichens in New Zealand. Its fruiting bodies are not flat discs like many other crustose lichens. They are raised, ringed structures with a central opening, like tiny volcanoes or miniature eyes. The rim is pale and often slightly crenulated (wavy), and the centre is dark, giving the whole structure the appearance of a tiny eye staring out from the bark. It is the lichen of the watching gaze, the one that seems to follow you as you move, the one that makes you feel observed.
The thelotrema lichen is a crustose lichen, meaning it grows flat on the bark or rock, like a crust of paint, rather than upright or leafy. Its body is a smooth, continuous crust, often forming circular patches or irregular stains. The apothecia are raised, ringed structures with a central opening, giving them a unique, eye-like appearance. Under a hand lens, the apothecia are beautiful, perfect circles with a dark centre and a pale, wavy rim.
Biologically, the thelotrema lichen is a partnership, a fungus and an alga living together. The fungus provides structure and protection. The alga provides food through photosynthesis. The apothecia are the spore-producing structures, releasing spores into the air through the central opening.
To find thelotrema lichen is to find the tiny eyes on the bark. It is pale, crusty, and watching, a living gaze on the tree. You have to look closely. You have to bring your face close to the bark. You have to let the lichen stare back at you. It is the lichen of the watching eye, the one with tiny, ringed openings like tiny eyes staring from the bark, the one that proves that the forest is watching you back.