Listen to this episode:

The Fifth Season

Broadcast on June 30, 2011

Cenizo and ocotillo put on a show during the rainy season. (Photo by Cathryn Hoyt)

Swallowtails "puddling" -- sipping salts from a damp patch of earth. (Photo by Cathryn Hoyt)

By Cathryn Hoyt

In the Chihuahuan Desert region, we spend fall, winter, spring and summer dreaming of and talking about our fifth season—the rainy season. Local wags will tell you it starts on July 4th—with a crash of thunder, a gust of wind, and a torrential downpour that causes Independence Day celebrants to scurry for cover and ranchers to sigh in relief. What does this fifth season’s arrival mean for our plant and animal neighbors?

Up to 75 percent of the Chihuahuan Desert’s annual precipitation falls in the summer months. This gift from the heavens results in a frenzy of friskiness, as plants and animals get on with the business of life.
The first hard rain brings out thousands of fuzzy, bright-red velvet mites with one goal in mind—finding a mate. The male mite is a gardener by nature, creating a “sperm garden” on small bits of plant material. But gardens need admirers, so he lays an elaborate silk pathway that radiates out from his garden. If a female encounters this path and finds it enticing, she’ll follow it to the sperm deposit and sit in the sperm, impregnating herself.

The female velvet mite can lay up to 100,000 eggs. The larvae from these eggs attach themselves to grasshoppers, beetles, butterflies, and other arthropods. They get their nutrients by sucking juices out of their unlucky hosts. After the larvae mature, they return to the soil, where they feed on insect and snail eggs, and other tiny arthropods—until the next year’s first hard rain prompts them to emerge, starting the cycle again.

Other creatures are drawn to the damp soil left behind by a passing thunderstorm. Male butterflies—especially swallowtails, sulphurs, and tiny blues—gather in masses at damp patches of earth, sipping salts dissolved by the rainwater.

This behavior, known as puddling, is believed to enhance male butterflies’ attractiveness and females’ reproductive success. Female butterflies lose a lot of sodium during the egg-laying process. And they’re too busy nectaring and laying eggs to hang around sipping sodium at the nearest mud puddle. Instead, they receive a nuptial gift of this essential mineral from males during mating.

Of course, insects aren’t the only ones feeling frisky during the rainy season. Summer rains bring out the very best in our desert plants. And some plants, according to old wives’ tales, can even herald the rains’ arrival.

The cenizo, often called the barometer bush, is said to put on a stunning display of purple to pink blossoms to announce the coming of rain. Not so fast, say the experts. Cenizo are most likely to bloom immediately after a rain, in response to high humidity and increased soil moisture. However—those same experts will admit—the cenizo can bloom in response to high humidity even before the rains begin.

The rains’ arrival also inspires scarlet bouvardia and yellowbells to splash our rocky hillsides with yellow and brilliant red flowers, framed by deep-green leaves. The beebrush, with its minuscule white blossoms, fills the canyons with a most exquisite fragrance. The sunset-orange of a flameflower, a tangle of tiny pink spiderlings, and sky-blue morning glories will challenge your whole sense of what a “natural color” really is.

Invite a friend to visit the Chihuahuan Desert region in August, and they’re likely to tell you that you’re nuts. Visit a desert in the summer? No thanks. But if you can convince them that our fifth season is the most spectacular, once here, they may never want to leave.

Have a question or comment about this episode? Contact Nature Notes Coordinator Megan Wilde at mwilde [at] cdri [dot] org. Or discuss this episode on Nature Notes’ Facebook page.

References & Resources for Educators

• Cenizo Journal: this episode was adapted from an article in the summer 2009 issue
• Rainbugs: from “Moseying: Exploring the Natural World,” an essay collection from the Sibley Nature Center in Midland, Texas

.