The Carlisle Mosquito Online

Friday, October 28, 2005



(Photo by Tom Brownrigg)

There are many fungi whose names lend themselves to the theme of Halloween. In past years we have featured Dead Man's Fingers, Witches Broom, and Wolf's Milk Slime. This year it's time for the Jack-o-Lantern or Omphalotus olearius.

When and where found: Tom Brownrigg called me on September 2 about a clump of mushrooms he saw at the base of an oak tree on North Road. Mushroom identification by phone is a bit tricky so I went to look at them. They were definitely Jack-o-Lanterns and I brought home a couple of specimens for reasons I will divulge in a moment. These mushrooms can supposedly be found from July through November. I tend to find them in August and September. The Jack-o-Lantern is a wood-decay fungus whose mushrooms are usually found at the base of hardwood trees or on old hardwood stumps. Sometimes, the mushrooms seem to be growing on the ground but they will be connected to buried wood.

Distinguishing characteristics: The cap of the Jack-o-Lantern mushroom is orange like a traditional Halloween pumpkin. The caps are smooth and might be anywhere from two to six inches across. They usually appear in large clusters — 50 or more is not uncommon — and they overlap one another. The gills are a yellow-orange color and they merge onto the stem and run down it a little way. The stems are a paler color than the cap and can be up to eight inches tall. The spores are creamy white. The most fun aspect of the mushroom is the reason that I brought some home. The gills glow in the dark. The light is not as bright as a firefly light but it is continuous and emanates from a much larger area.

Night light: David Arora in Mushrooms Demystified claims that the best way to see the glow is to sit in a dark closet with the mushrooms and eat a cheese sandwich to keep from getting bored while your eyes adjust to the dark. My dinner guests that evening took turns shutting themselves in a closet to look at the mushrooms. We skipped the cheese sandwich since it took only a few seconds for the green light coming off the gills to register. Fresh specimens that are actively producing spores glow more brightly. Marcia Jacob, a member of the Boston Mycological Club, has collected Jack-o-Lantern specimens on consecutive days in their development and observed that one and two-day old mushrooms do not glow at all. Three, four, and five day-old mushrooms glowed. The spores she collected from the mushrooms did not glow. The substances that cause the glow are luciferases which are waste products created by the fungus and concentrated in the gills. Tom was intrigued by a mushroom that glows and wanted to investigate the process further. The ones on North Road had turned to mush but I was lucky enough later in the month to find another clump along the trail into the Estabrook Woods at the end of Kibby Place.

Tom's story: "I was curious as to whether an instrument I use at Tufts University called a 'spectrofluorometer' might be sensitive enough to detect the luminescence, and also be able to record a 'spectrum' of it, which is a graph showing luminescence intensity versus wavelength. The instrument was indeed adequately sensitive, and the luminescence spectrum shows peak intensity at 550 nm, which to the human eye appears green, the color that Kay and friends observed. A second spectrum taken four hours later shows that the luminescence has decreased by about 30%."

Poisonous: Jack-o-Lanterns are poisonous and can make you very sick for several days. They smell good and some people are tempted to eat them but it's a serious mistake.

References: Tom Volk's website at; David Arora, Mushrooms Demystified; Alan Bessette et al, Mushrooms of Northeastern North America.

Submissions and ideas for the Biodiversity Corner are encouraged on any wildlife in town. Send a note to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to

2005 The Carlisle Mosquito