Yes! It’s true there is a firefly occasionally active in Bernheim Forest during the winter. However, unlike those familiar fireflies of summer that enchant us with their magical glowing lights, the Winter Firefly (Ellychnia corrusca) are only day active (diurnal) and are “lanternless” fireflies. This means they do not, in fact, physically can’t, light up like the amazing, glowing fireflies we see during the warmer months.
When you’re out hiking in Bernheim on a warm winter day, be on the lookout for this firefly crawling around on the south-facing side of oak, tulip poplar and certain hickory trees. Why the south side? In winter, we get more sunlight coming from the south direction and fireflies, like all insects, are cold-blooded and cannot generate their own body heat. They need the extra warmth of the winter sun in order for them to remain active.
For the Winter Firefly, which has carved out a special niche in nature by being active in winter when other fireflies are not, it makes perfect sense they would, over time, lose their lantern and their ability to light up. Even if the Winter Firefly had a lantern and the ability to flash or glow, winter nighttime temperatures would be too cold for them to remain active at night and make use of it. Keeping that ability would be a useless waste of energy.
If you’re curious what month Bernheim’s first flashing firefly make their appearance, stay tuned for an upcoming post for more information. Hint: it’s much earlier in the year than you would think!
If you’d like to experience the amazing world of Bernheim at night, check the forest echo (Bernheim’s quarterly newsletter, which is mailed directly to members and can be picked up at Bernheim) or our website for our many night programs offered.
-Bill Napper, Volunteer Naturalist