Friday, May 18, 2007

Fireflies

Driving along the levee road on warm, wet spring nights is a challenge. If I'm not dodging toads and frogs flushed out by the rain, I'm stopping every few hundred yards to move them 100 feet off the road. Of course, I know this is a temporary solution. Invariably, they'll hop right back into traffic.

If you drive over 30 mph, your windshield wipers quickly fill up with the bright yellow flickering lights of fireflies. When that happens, slow down and wait for the beetles to dislodge out of the wiperblades to continue their courtship until another, faster driver passes. It's probably a good thing I don't know my moths very well.

Fireflies are really common in most of rural Missouri, a state with thousands of miles of unpolluted rivers, streams and creeks. A member of the Lampyridae family, fireflies thrive in the leaf litter of moist woods along streambanks. In their larval stage, "glowworms" feed on earthworms, snails and slugs. With their sharp mandibles, larvae inject anaesthetic into their prey, thereby immobilizing it. Glowworms may, too, scavenge on dead snails and worms. Speculation holds that adult fireflies feed on plant nectar as well as other invertebrates.

Firefly flash patterns have been intensely studied and documented. Flashes occur when a substrate (Luciferin), combines with an enzyme (Luciferase), ATP (Adenosine triphosphate) and oxygen. Very little heat is given off during the flash; almost 100% of the energy is given off as light. Compare that to an incandescent bulb, where 90% of the energy is wasted on heat and only 10% comes out as light. The mechanism of flash patterns is under debate. A plausible theory suggests that a firefly can restrict or control the oxygen supply to the photic region of the tail end. Cells at the tail end, called tracheal cells, may release a messenger molecule which activates the production of oxygen, allowing the chemical process to occur.

Different species of fireflies have different flash patterns. Flashing is used not only as a warning signal to predators, but as a tool for mating. Males flash their species-specific flash to females who perch on nearby vegetation or on the ground. The female flashes back after a specific time delay; sometimes, a flash dialogue takes place before mating. Certain characteristics of male flash patterns (like increased flash rate or time delay) influence mating success, just as ornate male birdsong influences bird breeding patterns.

Females of one genus mimic the responses of other fireflies in the area. When a female attracts a male of another species, she will devour him, thereby gaining some of his light-producing defensive chemicals and making her signal stronger.

Countrywide, firefly populations aren't as stable as they are in Missouri. Polluted waters, widespread pesticide use which damages non-target organisms and light pollution are the three main factors causing their decline. Intense light interferes with the breeding firefly's ability to see flash patterns. If you're in a place with fireflies, you might notice they're not very active during the full moon.

Fireflies lay their eggs in moist soil with leaf litter. They like brushy, weedy areas not too far from a water source. So, put away the pesticide and don't mow as much. Fireflies won't be the only invertebrates who will appreciate it.

3 comments:

Anonymous said...

I'm frustrated. I've lied in MO the past 4 years and have yet to see any fireflies. I was so excited about moving back here from the West Coast to see them, but -- nope. I'm in Joplin, by the way, but also spent time in other parts of MO with the same result.

Allison Vaughn said...

Gosh, I wonder if historic prairie country doesn't have them? I would look for them around creekbeds. I would also recommend hitting an Ozark river in early to mid-June, preferably after a rainy spell to see them. I feel really bad for you! They're truly magical.

PegiAnne said...

I just saw my first fireflies of the year !