Faithful reader Ginny writes, "I love fireflies. How can I encourage them to come to my yard? Are they harmful to my garden?" Let Grumpy shed light on the matter.
Like many of you, Grumpy grew up to the delight of chasing fireflies (we called them lightning bugs) on warm summer evenings. We'd catch a dozen or so, drop them into a clear glass jar, and walk around with a bioluminescent lantern lighting the way. Of course, we ALWAYS practiced catch-and-release -- what kind of monster would want to kill such a cool bug?
Hundreds of different species exist, so the kind of firefly in your yard may not be the same in mine. They don't flash for fun -- it's strictly business, in the same way that other "ladies of the evening" leave a light on behind them in their windows. Males fly around and flash to locate females of the same species. Females resting on foliage, twigs, or grass flash back. If the flashing patterns match, he flies down to find her and engage in joie de vivre. What can I say? It's a flash dance.
Fireflies do no harm to people or wildlife. If anything, they threaten each other. Females of some cannibalistic species have learned to mimic the flashing patterns of males of other species. She flashes a come-on, he flies to her and flashes, "How you doing?", and she eats him. So sneaky, so amoral, so typical of females. Adults of other species, however subsist on pollen and nectar from flowers and some don't eat at all.
So what are some things you can do to make your yard firefly-friendly this summer?
Create a lush, moist environment featuring a variety of leafy plants of different heights. Fireflies are nocturnal. During the day, they hide from predators in the foliage of grass, low shrubs, perennials, and ground covers. You won't find many fireflies in a Wal-Mart parking lot. You will, however, finds lots of cars with their doors tied on.
Mow your grass high. Like I said, fireflies often rest during the day in tall, moist grass. If you buzz it all off to the ground every week, you'll chop up the fireflies resting there. If you're a lawn hater and wildflower meadows are permitted where you live, plant one.
Grow flowers. Their pollen and nectar feed some species of fireflies.
Turn off your outdoor lights at night. Fireflies flash to locate and signal each other. Your megawatt security light interferes with this. It also makes your sleep-deprived neighbors hate you and want to key your car.
Ditch the insecticides. Long-lasting insecticides sprayed on foliage kill them. If you spray your yard for mosquitoes, you'll kill the fireflies too. Wear insect repellent instead.