If you’re an Arizona resident, you’ve surely noticed the massive influx of caterpillars inching their way across lawns, roads, and sidewalks in recent days. And these aren’t just any caterpillars. They are big, fat, and colorful caterpillars measuring 2-3 inches long. These green-and-yellow southwestern crawlers will eventually become white-lined sphinx moths, one of the largest species of moth in the world.
The Copper Courier, a publication owned by Courier Newsroom, reports that the booming population of caterpillars is caused by recent monsoon activity. It’s been years since Arizona has had heavy rains, but now that the state is getting inundated, the caterpillars are taking advantage.
Arizona resident and entomology professor at UArizona Goggy Davidowitz told The Copper Courier, “when there is a good rain season, they (caterpillars) capitalize on that and they’re very prolific and they’ll put in multiple generations.”
The caterpillars are busier than ever. And now, they’re in what’s called a “wandering phase.” During this time, they search for a spot to burrow underground and pupate (go through the process of becoming a moth). As their search continues, residents will enjoy (or endure) more caterpillar-packed days.
Amazing or Annoying?
Researches are clear about their fascination with the recent caterpillar boom, but Arizona residents have mixed feelings.
“I know some people are absolutely freaking out,” Kelsey Shaw told Courier Newsroom’s publication, The Copper Courier. But Shaw and her two girls love the caterpillar craze.
“We actually homeschool, and in our curriculum, we were learning about butterflies and moths this week. It was perfect.”
But there are also downsides to making new caterpillar friends.
“It’s just been stressful when we’re driving,” explained Shaw, “because they (her kids) get really upset about running them over. We don’t want to hurt them.”
Driving down the highway during the caterpillars’ wandering phase is a sight to behold, as thousands of the crawlers attempt to make their way to the other side. Sadly, many fall victim to traffic, leaving behind nothing but a splotch on the road.
Roads aren’t the only places you’ll see these colorful caterpillars. They’re showing up everywhere—gardens, walls, swimming pools, and hiking trails—in their search for food and a pupation location.
The Need to Feed
Before the white-lined sphinx moth caterpillars are able to pupate, they need to load up on fuel by eating everything in their path.
Doctoral student in entomology at the University of Arizona Sarah Britton explains that these caterpillars can be found around plants, munching away. They eat and eat until they become quite large…and then they just keep eating.
After about three weeks of snacking, the caterpillars will be ready to enter the pupation phase, which lasts another three weeks. That means Arizona residents may experience a brief respite from the caterpillar invasion before the pupation phase ends and the white-lined sphinx moths emerge from the ground.
“This species is the most abundant hawk moth in all of North America,” Davidowitz said. “But the highest abundance (is) in the Southwest, they have evolved into semi-arid environments.”
Once the sphinx moths emerge, they will go on to live for only 7-10 days. But despite their short lifespan, they will be hard to miss. These super-sized moths are often mistaken for hummingbirds due to their incredible size and their ability to hover as they feed.
An Important Role to Play
Hawk months are not just an interesting phenomenon in Arizona. They also play an important role in the ecosystem of the Southwest, as reported in The Copper Courier, a Courier Newsroom publication.
These moths are efficient pollinators, and they play an important role in pollinating plants in the state. Britton and Davidowitz explain that this type of moth is known as a “generalist” species, meaning it can consume and pollinate a wide variety of plants.
Davidowitz continued: “Another cool thing about this species is all hawk moths are nocturnal, so they fly at night. They will pollinate with both night blooming flowers and day blooming flowers.”
White-lined sphinx moths are quite resilient, but they still need monsoons to survive. This has researchers worried, as rising global temperature may threaten the species.
Davidowitz lamented that the caterpillar and moth populations in Arizona have steadily declined over the past two decades.
“Last year, we found when we went out black-lighting, it was a drought year, we got almost no hawk moths at all,” he said.
But for now, the harmless caterpillars and moths are back in record numbers. Researchers like Davidowitz and curious nature lovers like Kelsey Shaw and her daughters are hoping that this will be far from the last caterpillar boom in Arizona.
This story was originally published by The Copper Courier, a publication owned by Courier Newsroom.