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New Mexico State University

New Mexico State University

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Caterpillar Invasion No Cause for Concern

LAS CRUCES - Large numbers of caterpillars crawling across roads in southwestern New Mexico are no cause for alarm, a New Mexico State University entomologist said. The insects usually feed on native rangeland plants such as purslane but begin moving when they run out of food, said Carol Sutherland with NMSU's Cooperative Extension Service.

"They are roaming around looking for other places where there's food," she said. "They're crossing highways, sometimes in large numbers, making people stop and wonder. There is no cause for concern."

White-lined sphinx caterpillars can grow to be four or more inches long and are yellow with long black or brown bands or stripes on their bodies. They also have a large horn extending off the back or rear of their abdomens.

Sutherland said the timing of recent rains has resulted in an unusually high population of these caterpillars.

"They do feed on a lot of weeds and they may move into some of your backyard vegetables or your blooming plants and might do a little damage," Sutherland said. If so, contact the county Extension office for safe pest control recommendations.

According to Sutherland the moths from these caterpillars mimic hummingbirds. They are strong fliers and move along waterways such as canals and ditches. They can lay anywhere from a few hundred to a thousand eggs, producing three to five generations in a year.