Bio Bits - The Secret Code Of Fireflies

We have all enjoyed the spectacle of fireflies flashing on a warm summer evening. A dark woodland edge or open meadow full of hundreds of tiny flashing lights is a magical sight indeed. But you have to wonder -what are these insects up to? 

First, fireflies are not flies at all, but soft-bodied beetles in the family Lampyridae. Most of the over 100 species found in North America are luminescent, producing a chemical light that is so efficient it wastes no energy in the form of heat. One, two or three segments near the tip of the abdomen give off the light; when they are not lit they appear paler than other abdominal segments. 

The luminescent fireflies are nocturnal and are active mainly around dusk. Each species inhabits a particular habitat and is active at a certain time of night. And - this is the cool part - it has its own distinctive series of flashes. 

This series of flashes is like a secret code that the male fireflies use to signal the females of their species, enabling the males and females to find each other to mate. Typically, a male flashes his signal while in flight to attract a response from a female on the ground. When she signals back, the male flies to her. There are females of some species, however, that will answer the signals of other species’ males. Their mimicry entices these males to fly in for a closer look, whereupon the female captures and eats the unsuspecting male. 

Firefly eggs are laid in moist soil or rotting wood and hatch in about a month. The larvae are nocturnal carnivores, eating small insects and snails. When the weather cools they burrow underground to spend the winter, emerging again in the spring. If you happen upon a firefly larva (or even an egg) you will know it since they are luminescent as well. Look for these glowworms in the evening on the ground in damp, marshy areas.

Submitted by Cindi Kobak

Images: Wikipedia

(From the July 2014 Newsletter.)

Citizen Science: Firefly Watch

Are fireflies disappearing?

Spotting fireflies is a special part of warm summer nights, but lately, they seem to be disappearing from our landscape. The Museum of Science, Boston, has teamed up with researchers from Tufts University and Fitchburg State College to set up Firefly Watch to track the fate of the amazing insects. With your help, they hope to learn about the geographic distribution of fireflies and their activity during the summer season. Fireflies also may be affected by human-made light and pesticides in lawns, so they hope to also learn more about those effects.

It’s easy to participate in Firefly Watch. Basically, they want to know if you have fireflies in your backyard this summer (or in a nearby field if you don’t have a backyard). Even if you don’t see fireflies, your data is valuable.

You will join a network of volunteers to observe fireflies in your own backyard. Tracking your progress online and interacting with fellow Citizen Scientists, you will help scientists map fireflies found in New England and beyond. You do not need specific scientific training and participating in Firefly Watch requires just a fraction of your time. 

To participate you should be able to spend ten minutes checking your backyard for fireflies, one evening a week throughout the summer. However, the researchers realize that you lead a busy life and may not be able to collect data every week. Any information you can send in is valuable, as long as you fill out the observations form, and upload the results.

There is much that we still don’t know about what ecological and human-made factors affect firefly populations. The data you collect for Firefly Watch can help the researchers gain a better understanding of how the following elements influence the fireflies in your neighborhood.

To be most useful, a habitat site should be fairly small and cohesive. It should be no larger than the area you can see easily while standing in one spot. A backyard that includes shrubs and trees can be considered one habitat, but a pasture bordering that yard would be considered a different habitat.

Researchers are interested in several environmental factors that may affect fireflies. 

Mowing - During the day, fireflies can spend a lot of time on the ground and may be susceptible to frequent mowing.

Fertilizer - Researchers don’t know what effect fertilizers have on fireflies. Many fertilizers contain both weed killers and pesticides.

Weed killers - The effect weed killers (herbicides) have on fireflies is not known.

Pesticides - People apply pesticides to control insect pests, but pesticides also kill many non-pest insects. Firefly larvae — young fireflies — are not pests, but they are grubs that live in the soil and will come in contact with lawn pesticides, which target grubs.

Adult fireflies may come in contact with sprayed pesticides, some of which are used on localized problem areas like trees. Others, like those targeting mosquitoes, are sprayed over a large area. Although it may seem reasonable to assume that pesticides have an adverse effect on firefly populations, we need data to prove or disprove this assumption.

House or Building Lights - Most fireflies find a mate by flashing. They must be able to see the flash of a prospective mate and return the flash. We don’t know to what degree outside lights affect a firefly’s ability to locate a mate.

Streetlights - Streetlights produce a type of light different from house lights, and we’d like to determine if one type of light is more detrimental than the other.

Nearby Water Sources - Firefly larvae live in the soil, and they need a certain amount of moisture to survive. In some areas, rainfall and shade may be enough to keep the soil moist. In others, the moisture may come from standing water, but we don’t know how important standing water is to fireflies’ survival, nor do we know how different types of water affect them.

For more information visit the Firefly Watch website at legacy.mos.org/fireflywatch/.

(From the July 2014 Newsletter.)