The American Snout butterfly has a reputation for “mass movements” in and around Central and South Texas following late summer rains.
The American Snout butterfly has a reputation for mass movements in and around Central and South Texas following late summer rains. Credit: Bonnie Arbittier / San Antonio Report

Monarch butterflies will be beginning their migration soon, but in the meantime, another orange-and-black butterfly has arrived in droves.

The American Snout butterfly has been moving up the Interstate 35 pollinator corridor, clogging windshields and car grills along the way.

The long-nosed butterfly with mottled black, orange, and white coloration has a reputation for mass movements in and around Central and South Texas following late summer rains, according to local biologists and butterfly enthusiasts.

“It’s not a real migration,” said Luciano Guerra, outreach coordinator for the National Butterfly Center in Mission. The snouts are opportunists, seeking their host plant and looking for mates.

Snouts, so-called because of their tubular, elephant trunk-like “noses,” lay eggs on the leaves of hackberry trees. The drought-tolerant tree is often considered a trash shrub, but its leaves provide food for snout caterpillars and its berries offer important winter sustenance for birds. Large snout caterpillar populations can completely defoliate a hackberry tree, but the tree will recover.

Local news is at the heart of democracy.

Our newsroom works on your behalf to hold officials accountable. But we can't do it alone. We rely on membership donations from readers to support our fact-based reporting. Will you join us and donate now?

Larry Gilbert, professor in the Department of Integrative Biology at the University of Texas at Austin, expert in biological diversity and longtime snout follower, has been watching snouts since he was a kid in Laredo. He cites an incident in the 1970s in which successive rains broke a long drought.

“There were hundreds of snout pupae hanging on every hackberry bush,” said Gilbert. “They defoliated every hackberry. Ranchers were flummoxed and didn’t know what was going on.”

In the adult butterfly stage, snouts take nectar from various flowering plants and live about two weeks. The insects disguise themselves as dead leaves when their wings are closed. With wings open, they flaunt their orange, black, and white accents and are sometimes confused with monarchs or painted lady butterflies.

When dry weather occurs and hackberries retreat into dormancy, the snouts also start to shut down, said Gilbert. They go into a kind of hibernation, he explained, waiting for the rains.

“When you see a big bullseye over South Texas brush country with four-five inches of rain? Ok, you’ll be breathing snout butterflies in a month,” he said. Gilbert believes there will be more frequent snout invasions than in the past. “It used to happen every eight years or so,” he said. “Now we’re seeing this pattern every two, three years.”

Around June 20-21, rainfall exceeded 18 inches in some parts of South Texas. That likely started the cycle. A few weeks later, San Antonio got several inches of rain around July 4. Three weeks later, the snouts appeared.

Gilbert said snouts typically gravitate to ditches, moist areas, and streams and wait for the rains so they can reproduce. “Their main goal is to make more snout butterflies,” he said.

At the Nueva Street dam in Southtown near downtown San Antonio recently, hundreds of snouts gathered at the dam release.

“We’ve had lots of them feeding on the frogfruit in our landscaping recently at the San Antonio River Authority Environmental Center,” said Lee Marlowe, sustainable landscape ecologist for the river authority.

Texas Parks and Wildlife Department biologist Tony Henehan reported recent heavy populations of snouts in the Rio Grande Valley.

“All of South Texas reported seeing thick swarms of them, colorful clouds of them!” said Mariana Treviño Wright, executive director of the National Butterfly Center.

In the annals of American Snout butterfly migrations, 1921 ranks as a most remarkable year. After a record downpour in Central Texas on Sept. 9-10, 1921, when 36.4 inches of rain fell in an 18-hour period, a snout butterfly breakout resulted a few weeks later.

“An estimated 25 million-per-minute southeasterly bound snout butterflies passed over a 250-mile front from San Marcos to the Rio Grande River,” according to Mike Quinn’s Texas Entomology, a source for Texas insect news and info. Scientists noted at the time that the butterflies’ flight “lasted 18 days and may have involved more that six billion butterflies.”

 

Monika Maeckle

Monika Maeckle

Rivard Report co-founder Monika Maeckle writes about pollinators, native plants, and the ecosystems that sustain them at the Texas Butterfly Ranch website. She is also the founder and director of the Monarch...