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Pyractomena firefly

Sex, Lies and Fireflies

Thursday, July 5, 2012

There is nothing more peaceful than paddling down the river on a July night, watching the stars twinkling above and the fireflies twinkling below. Nothing more peaceful to me, that is. Not to the fireflies. For the fireflies, serious business is afoot. Business fraught with danger.
Fireflies are beetles, not flies, as their name implies. They are creatures of the night. As such, all their business must be carried out in the dark. This presents a problem when it comes time to find a mate. Crickets and grasshoppers find their mates by their song. Many moths use a type of perfume, called pheromone, to attract their mate. Mosquitoes rely on the buzzing of their wings. Fireflies attract their mates with their flashing lights.
A specialized tissue in the abdomen of the firefly produces chemicals that, when mixed together, produce light, much the same way a light stick works. Both the male and female fireflies can produce light. There are many different types of fireflies, and each produces a characteristic flash pattern. The patterns may differ in color, numbers of flashes, duration of each flash and length of time between the flashes. With a little practice, you can learn to identify the different species by their flash.
The male will fly along the field or marsh emitting his flash. The mating firefliesfemale spends her time waiting on the ground or on a plant. When she is ready to mate, she will answer the male by emitting her flash, which is different from the males flash. The male sees the female flash, lands and mates with her. The males far outnumber the females, so it is a race to be the first to find the females.

If this were the end of the story, what a great life it would be to be a firefly. But the story continues.

There are a number of different groups, or genus', of fireflies. Two of the groups have similar names, so be sure to keep them straight. Photinus fireflies are about half the size of Photuris. An easy way to remember them is Photinus is the tiny firefly.

After mating, a female of the genus Photuris will sit on a plant, with her head up and jaws open. Photuris firefly

When she sees a male Photinus firefly flash, she imitates the female Photinus. The male sees her and thinks he has found a receptive female to mate with. Imagine his surprise when he finds not an eager mating partner, but a much larger Photuris firefly. Of course, she has no interest in mating with him. Instead, she pounces on him and eats him! So much for his romantic evening.
Some Photuris fireflies can imitate the flash of over a dozen other species of fireflies.

The Photinus males have a problem. If they rush to mate with a blinking female, they could be devoured by an imposter Photuris. If they hesitate, they could loose their chance to mate with a legitimate Photinus female to a quicker, less cautious male.. Many species of Photinus fireflies mate at dusk. This allows them to locate a female by her flash, then approach close enough to look at her to make sure she is the same species.

Occasionally, a female Photuris firefly will give off an extra blink when trying to imitate a female Photinus. This mistake will cost her a meal because it will scare off all male Photinus. Some males will use this faulty blink to their advantage. When approaching a female, the male Photinus will imitate a female Photuris, faulty blink and all! Other males will see this, think it's a deadly Photuris female and stay away. This allows the first male to approach slowly, giving him enough time to decide if the female he responded to is in fact safe to approach.

Not all female fireflies sit patiently on the ground waiting for a male to approach. Sometimes a Photuris female will locate a flying male Photinus and attack him in the air. A male Photuris may use this to his advantage to find a mate of his own. He may imitate the male Photinus, stimulating an attack by a female Photurs. When she approaches, he grabs and mates with her. This, however can be a risky business since the female is intent on eating, not mating.

Firefly adults are not believed to feed, except for this predation by Photuris of other fireflies. So why does she feed on them?
Fireflies are easy to find. Just look for the flash and you have found a firefly. Fireflies are also easy to catch, being slow fliers. Since they don’t hide and can’t move fast, they must have some other way to protect themselves from their enemies. This they do by bleeding. When attacked, fireflies will bleed from their joints. This blood is poisonous. Many nighttime predators soon learn to leave the blinking insects alone. This poison not only protects the fireflies, but their eggs and larvae as well. And just like the adult, the eggs and larvae can also give off light.
Photuris fireflies don’t make the poison. The only way they can get it is to eat the other fireflies and sequester the poison in their blood. Once they have done this, they, their eggs and larvae are now protected by the poison.

As you can see, a firefly meadow is not a peaceful place at all. It is filled with sex, lies and fireflies.

If you would like to learn more about fireflies and help scientists collect data to determine if fireflies are disappearing from the landscape, check out the Firefly Watch Citizen Science project at