One of the mysteries and delights of a summer’s eve is to watch Mother Nature’s version of “Light My Fire”. No, this is not the performance you first heard in 1967 by the Doors or a year later when Jose Feliciano took it to number three on the charts. This “Light My Fire” is performed by millions of lightning bugs, aka, fireflies, in people’s back yards at dusk across eastern North America. The performance will be replayed each evening for several weeks. Lightening bugs are not “bugs” at all. Entomologists reserve this term for the “true” bugs with sucking mouthparts and incomplete metamorphosis like stink bugs, boxelder bugs, and their kin. Lightning bugs are beetles that have evolved a clever means of communication. They emit flashing patterns of eerie greenish or yellowish light. Light is produced by specialized cells in the abdomen of the beetle. These cells contain a chemical compound called luciferin. An enzyme called luciferase breaks down luciferin and a flash of light is emitted. This remarkable reaction takes place with the production of virtually no heat and is a true marvel of chemistry.
So, what is all this flash-dancing about? In a previous Bug of the Week, we talked about the wicked lightning bug femme fatale, Photuris (NEED LINK TO JULY 4TH, 2005). She mimics the flash pattern of other species of lightning bugs. As hopeful males fly about looking for flashes of a mate, they are attracted by the flashes of Photuris. After luring them near, she shares a meal with them. Unfortunately, the unsuspecting male is the meal. This week I observed male lightening bugs in the genus Photinus making low flights just a few inches above the grass in lawns and meadows. As the males patrolled, they produced brief flashes of light. Sometimes, a female Photinusresting in the grass below would respond with a flash of her own. The lucky male would alight in the grass and a series of sort flashes would bring the couple together.
In a series of fascinating studies, Dr. Sara Lewis of Tufts University and her colleagues have unveiled many mysteries surrounding lightning bugs and the evolution of their courtship behaviors including their flashing lights. They discovered that in addition to supplying sperm to fertilize the eggs of the lightning bug lady, the male also provides a packet of rich protein used by the female to provision eggs developing in the female’s ovaries. This nuptial gift is important for the reproductive success of both the male and female lightning bug. Dr. Lewis and her colleagues also discovered that in the lightening bug world, much like our own, it is the males that do much of the displaying and the females that do much of the choosing. Females differentially select suitors on the basis of their bioluminescent displays. In some species of lightning bugs, the duration of the flash is an indicator of the size of the nuptial gift and the female responds favorably to guys with longer flashes. In another related species, guys with more flashes per minute were more likely to be answered by females. So men, to take a lesson from the lightning bugs, if you really want to light her fire, shine your love light long and do it often.
We thank Sara Lewis for being the inspiration for this Bug of the Week and for taking time from her busy schedule to enlighten us. To learn more about lightning bugs, please visit the following web sites.