They’re irresistible to children, but their flashes can enchant an observer of any age. Fireflies seem like magic. They’re mostly associated with sultry summer nights in the eastern U.S. But they are found in the arid West, including in our region.
Now, biologists, with help from the McDonald Observatory, are working to understand and preserve the mysterious lightning bugs of West Texas.
Candace Fallon is a biologist with the Xerces Society for Invertebrate Conservation.
“There's just something about fireflies,” she said. “People love them and think they're so special, but I just think there's this strange disconnect about thinking of them as imperiled insects.”
Fallon’s group fights for freshwater mussels, for bees, butterflies and other pollinators and – for lightning bugs.
That work began in 2018, amidst rising anecdotal evidence of firefly decline. Fallon and her colleagues assessed conditions for 132 firefly species. They found that a third were at risk of extinction, and at least 18 qualified as threatened or near-threatened.
One of those 18 is the mysterious sky island firefly. It’s known only from the Davis Mountains, from Alpine to Kent.
Lightning bugs need moisture, and in the West, most are bound to springs or perennial streams. The sky island firefly is different – it’s been spotted along Limpia Creek, but also on the dry summits at McDonald Observatory.
Pesticides and habitat loss imperil many firefly species. But for the sky island firefly, the main threat is that its dry homeland is becoming even drier.
“Drought was such a big element for us,” Fallon said. “And then, there's just a lot more oil and gas mining operations in those areas that seem to be putting pressures on some of the natural areas, and also potentially having impacts on the water table.”
The sky island firefly was first described in 1927, and it was identified not only in West Texas, but in northern New Mexico and southeastern Arizona. Fallon said the New Mexico ID was likely erroneous, and recent searches in Arizona have come up empty. When Fallon’s team searched in the Davis Mountains several years ago, they didn’t find a single sky island firefly.
But the creatures certainly endure. McDonald Observatory staff have spotted sky island fireflies and have collected data on their distinctive flashing pattern.
And Fallon’s West Texas expedition wasn’t fruitless. Her team made a side trip into the Chinati Mountains. There, they found a canyon luminous with fireflies.
“And there were tons of them,” Fallon said, “and we saw lots of larvae as well. They were all flashing, and the larvae were all glowing. And I think it might be an undescribed species. It was cool.”
They spotted another unknown firefly on a drive through Musquiz Canyon, south of Fort Davis. And Fallon said fireflies have been reported from the Guadalupe Mountains – the identity of those lightning bugs is likewise a mystery. Far West Texas, it seems, is a firefly terra incognita.
Firefly luminescence is haunting – but it also allow the beetles to ward off predators, and find mates. Light pollution is everywhere a threat to fireflies. Limiting outdoor lighting, and even taking the simple step of drawing curtains at night, is a boon for the bugs.
Xerces has a citizen-science initiative called the Firefly Atlas. Fallon urged West Texans to look for lightning bugs on summer nights, and to share what they see at fireflyatlas.org.
“I think we just have so many fewer eyes on the ground in West Texas,” she said, “and there is really a lot of discoveries to be made. And I think it would be really neat to have people out looking.”
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