The brightest nights in the forest are under a full moon in winter, after the leaves have fallen.
On magical moonlit nights when there is snow on the ground, you can wander the woods with little visual impairment. But in the summer, when the darkness is cloaked with extra layers of foliage and humidity, the Blue Ridge night comes alive with bioluminescence. Aside from the brightest fireflies, most of these sources of glow can only be seen in the darkest conditions, walking without a light, and with eyes that are fully adjusted to the dark.
Lightning bugs and fireflies are the most dramatic of our natural lights, but there are several other living things that light up the forest. Foxfire is glow-in-the-dark wood, rendered visible by the mycelia of certain species of fungi. Other fungi have illuminated fruiting bodies (bioluminescent mushrooms).
Jack-o-lanterns (Omphalotus illudens) are our most famous glowing mushrooms, but they are rather dim compared to bitter oysters (Panellus stipticus), our brightest. Bitter oysters begin emerging in July, but they become quite abundant by early fall.
Unlike jack-o-lanterns, which make a dramatic appearance even during the day (they are bright orange, quite large, and often grow in enormous clusters), bitter oysters often go overlooked during the day. They are small off-white gilled mushrooms that grow on twigs and logs. They are rarely noticed, but are quite attractive if you look at them closely.
A mushroom's raison-d'etre is as a spore dispersal mechanism for a fungus. Many of them are quite good at ejecting spores on their own, sending them into the winds and rain (think puffballs). Some mushrooms rely on critters to aid in spore dispersal, much like a flowering plant will use pollinators to spread their pollen, or entice animals to eat their fruits to spread berries. Like flowers, some mushrooms attract insects with their colors and some with their odors; a few species glow in the dark. It is now assumed that mushrooms glow in order to attract insects.
I've recently begun trying my hand at photographing bioluminescence. Notice the spider in the above picture, lying in wait for insects who are attracted to the glow of bitter oysters. And you thought jack-o-lanterns presented a halloween scene? Below is the same cluster of bitter oysters illuminated with a flashlight.
If I'd been walking in the woods with a flashlight, I never would have noticed the bitter oysters, but because they glow so brightly in the dark forest, it's one of the few things that you can see at night without a light. The cool thing about exploring the forest at night without artificial light is that you never know what you'll find. This is how I initially learned about blue ghost fireflies many years ago. A few years ago I saw some tiny glowing mushrooms on the bark of a black locust tree. I didn't know at the time, but it seems that this is either a species new to science, or a species that has never been observed bioluminescing. But recently I've seen them again, this time on a white ash, and I've now been able to photograph them.
They are super small (just a couple millimeters tall -- see pic of a relatively "large" specimen below). I've sent samples to mycologists, hoping to find out what they are. I'll keep you posted.
