Cynwyd Trail Night Walk
Join photographer George Manos and biologist Karen Snetselaar July 16 for a night walk on the Cynwyd Heritage Trail. The walk starts at 8pm at the Barmouth trailhead. We'll listen for night insects and birds and look out for fireflies and other luminescent creatures. Photographers, be sure you can use a manual shutter setting for long exposures under low light conditions. George has provided more details for the special requirements for firefly photography.
More about fireflies that we might see:
More than 2000 different species of firefly have been named, with over 150 being seen in North America. These members of the beetle clan include some that only glow in their larval stage--known as glowworms. A common species that we'll see is Photinus pyralis, the common eastern firefly, also commonly known as the big dipper firefly because of the males flashing pattern--a long flash while the insect moves forms a j-shape. Beyond that, identification of different firefly species is not a trivial undertaking. Males and females may have different flashing patterns, and males may flash differently when they are just cruising as to opposed when they have detected the presence of a female. Females of many species stay attached to vegetation, with only the males being airborne. The figure to the left, from the Field Guide to Western North American Fireflies, shows a convenient way to represent this complexity.
Photuris pennsylvanica, the Pennsylvania firefly, was named the state insect after a campaign by Upper Darby students in the 1970's. Generally the flashing patterns of this and related species consist of one or two flashes.
Now for the really weird part
You might wonder about how using the biochemical process of producing light ever evolved in the first place. Many fireflies make toxic compounds, and it is thought that the light was a way to alert predators not to eat them--same idea as the bright color of monarch butterflies. Using light to attract mates evolved later. But some fireflies that don't make the toxic compounds have evolved a way to get some anyway. After female fireflies in the species Photuris versicolor have mated, they no longer respond to mating signals from their own species. Instead, they flash patterns that attract firefly males of different species. If the males are fooled, the female kills them and eats the part of the body with the toxic compounds. She can pass these along to her offspring, which will thus be protected from the predators without having to make the chemicals themselves. Read more about this amazing story in an article about famous scientist Thomas Eisner, to the left.
More references and information about the effects of darkness on plants and animals on the trail
Many living things are impacted by the increase in artificial light that lights up the night all over the world. Many plants use the length of the dark night to control developmental processes. For example, as the nights get longer in late summer, trees use this is a signal to start preparing for winter by withdrawing nutrients down into the soil and preparing to drop their leaves. If the darkness is interrupted by artificial light, some species don't prepare properly and they may be more vulnerable to damage from cold temperatures. This article from Purdue University has a good explanation of how plants do this, as well as a list of which trees are most vulnerable to damage caused by artificial night lighting.
