Even insects can't seem to resist the urge to explore.

Pioneering its way northward, the praying mantis began arriving in southeastern Idaho about 10 years ago. Stagmomantis californica came from northern Mexico and Southern California, adapting to colder winters along the way."The large praying mantis that most people are seeing is relatively new to Idaho," said Robert Anderson, an Idaho State University biology professor. "It's moved up from the South along the west side of the Rockies."

Anderson has been tracking the northward movement. During the past decade, people have brought him praying mantises to identify from Provo, then from Salt Lake City, Ogden and Malad, Idaho. Then he began finding praying mantises in his own back yard.

The 3 1/2- to 4 1/2-inch-long insects have not arrived sooner because cold weather killed their eggs.

"Who knows when or how," Anderson said, "but through a series of mutations, variant forms of this species have adapted to cold conditions."

About 50 to 150 eggs spend the winter in a protective casing called an ootheca. The eggs hatch from the ootheca in April and May.

A praying mantis is a gardener's best friend because of its diet.

As a youngster, it gobbles aphids, scale insects or mites. Five molts later as the mantis enlarges, it eats increasingly larger insects, including grass-hoppers.

"They do a wonderful job," said Bill Mayes, nursery manager at Pocatello Greenhouse. "Some people just don't like them because they look scary, but they're really beneficial."

The praying mantises are remarkable, not only for their ability to adapt to colder climates, but for their anatomy, too, Anderson said.

Their head can pivot 180 degrees.

"Most insects have to turn their whole bodies," Anderson said.

Their most popular trait is their front legs that are always cocked slightly and touching each other, making them look as if they're in a constant state of prayer.

The mantises' northward movement isn't their only mystery. They change colors from green to tan. It's partially due to sexual dimorphism, Anderson said. But researchers still aren't certain if the color diversity is due to plant color or shorter day length and cooler night temperatures.