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Question of the Week © 2017 Mike McGrath
Note: Hundreds of Mike's informative articles are available (in alphabetical order!) right here at the Gardens Alive website. To find Mike's answers to your specific garden problem, Click here and find your topic (like Weeds, Worms, Rhododendrons...) in our complete alphabetical archive of Questions of the Week.
Can we Re-Populate Our Lightning Bugs?
Very Special Q: Most listeners who write in about fireflies/lightning bugs just report that they seem to see fewer of them each summer. But back in 2011 (soon after we did our first big Question of the Week about the wonderful bio-luminescent creatures), Sharon in South Brandon, Florida (just west of Tampa) wrote: "Is it possible to purchase larvae to reintroduce lightning bugs to an area? We have many wonderful boggy, natural areas that would provide a good home for lightning bugs. Is it possible to purchase their larvae to 'seed' this area again? They once were prolific here, and I suspect that many years of spraying for fruit fly control did them in. But today there's not an orange grove in sight—so maybe they'd have a better chance now."
A: Is such a thing possible? We are strongly in favor of purchasing and releasing long-term-proven beneficial insects like lacewings to control pests, but there have been a few unintended consequences with lesser-controlled beneficial releases over the years. For instance, the multi-colored Asian ladybug that's currently invading people's homes for the winter was originally released in Pennsylvania for control of aphids and other soft bodied pests. (But the native 'convergent' ladybugs that gardeners can buy commercially are 100% beneficial and totally non-pestiferous.)
Before stricter controls on beneficials were enforced, Asian praying mantises were released to control pests and were SO successful that they out-competed the native American species. (So they didn't become 'pests' but they did take over.) And don't mention the words 'cane toad' to folks in Florida….
But the tropical biologist I interviewed for that previous Question of the Week, Dr. Fredrick Vencl, a researcher at New York's Stony Brook University and The Smithsonian's National Museum of Natural History, says that research on raising lightning bugs for release IS ongoing—and most of the domestic research he's heard about utilizes the species known as "The Big Dipper' Firefly, whose release would cause no harm as its already the most common native American species. (He calls it 'dirt common' in the US.) And to my Philadelphia born-and-bred chagrin, it's even the one I'm most likely to see here in Pennsylvania.
…Not the famed 'Pennsylvania Firefly'…
Nope. In fact, that firefly is even in a different genus. (Common names can be very cruel in entomology.) Anyway, Dr. Vencl says that a guy in Chicago is working on breeding the Dippers for sale, but the work is hard. Every entomologist I've spoken with has emphasized that we just don't know much about their larval stage underground. But Dr. Vencl did specify that the perfect place to release them once large-scale breeding is successful would be "an old abandoned farm; a mosaic of fallow fields that transition into woodlands".
So now we're throwing open space and farmland preservation into the mix, because preserving an old farm and letting it go wild would create the ideal "Photinus Park".
OK—so let's review what lightning bugs need to live long and prosper!
Actually, as with a lot of insects, the adults don't live very long—just two to three weeks. And any aerial spraying during that time—for pests like fruit flies or mosquitoes—would be devastating. In addition, the females need to be able to move up and down grasses or grass-like plants that are one to three feet tall; Dr. Vencl says that low-growing native grasses would be ideal. As is darkness; adult fireflies avoid areas with artificial light when they're mating.
…And if you do provide all those things, look carefully on the ground during a moonless night shortly after the adult light show starts to peter out; you might see the eggs of the next generation glowing on the ground. How cool is that? Then the eggs hatch into larvae, which feed on slugs, snails and earthworms. You might see these creatures on the surface of the soil in the fall if your timing is perfect, but for most species, most of this stage of life is spent underground.
Now, Dr. Vencl emphasizes that fireflies in the American South—and sub-tropical areas all over the world—are under a dramatically increased risk of pesticide exposure with the increased recognition of mosquito-borne diseases like the Zika virus. So it's vitally important that people trying to re-establish firefly populations advocate for and emphasize mosquito-specific prevention tactics.
Like emptying outdoor containers, scrubbing the sides of outdoor containers, and treating standing water with BTI—which only affects mosquitoes and other members of the fly family. Because despite their common name, we need to emphasize that fire flies are actually beetles; and aren't affected by fly-specific treatments like BTI, which is critically important, because both insects are moisture-loving creatures.
Dr. Vencl's bottom line:
Turn off outdoor lighting all together or at least place lights close to the ground; don't use pesticides other than BTI; and "don't be so fussy. Leave nooks and crannies of wild areas, use lots of native plants and allow areas to stay naturally damp. Don't drain ponds or low areas that are occasionally wet."
And that's where using BTI as a larvicide can really come in handy. People need to realize that they can control their mosquito population by treating wet areas with BTI and still work towards restoring their annual lightning bug show.
Special thanks to Cathy Jordan, Coach of the Lighting Bots FIRST Lego League team and her team-member students at Maranatha Christian Academy in Brooklyn Park, MN, for getting us started on this topic. To hear Mike's interview with Cathy and the kids—and his interview with Karen Verderame, Invertebrate Specialist for the Academy of Natural Sciences of Drexel University on the beautiful Ben Franklin Parkway in Philadelphia, listen to the special 'all lightning bug' edition of You Bet Your Garden show at http://whyy.org/cms/youbetyourgarden/all-about-fireflies/.