If you are a snowbird, this March is too early to leave the desert. The annual wildflowers don’t begin to bloom until early March, the cacti not until April. And this year has had copious rainfall, which will produce a bonanza of wildflowers, which will erupt when conditions are just right. They must produce flowers to attract the bees, bats, hummingbirds, and butterflies that will pollinate them. They rush to produce seeds in such abundance and with the right timing so that they will ripen and be ready to germinate when the summer deluges drench the dry, parched land.
Flamboyant, neon-colored flowers bring splashes of brilliant color to the desert, sweet, intoxicating fragrances waft through the air, and inebriated pollinators, coated with sticky pollen, flit in an excited frenzy from flower to flower. Night blooming cereus, saguaro, prickly pear, the chollas, agaves, yuccas — all pick this season to bloom.
Some of the desert’s most mysterious and unusual natural events occur during this season, after the snowbirds have disappeared. For instance, the unusual symbiotic relationship between the southwestern yuccas, the Mohave (photo) or Spanish Bayonet (Yucca schidigera), and the Torrey (Yucca torreyi), and with the tiny, white-winged, black-eyed Pronuba moth (genus Tegeticula), the exclusive pollinator of the yuccas. Without them, the yuccas would become another tick mark on the Extinct Species list. Likewise, the Pronuba moth’s survival depends on the yucca, on which she lays her eggs — again, exclusively.
In one of the unanswered mysteries of the natural world, the moth’s internal alarm clock rings and she emerges from her cocoon at the exact time that the yucca blooms in early spring, which is always dependent on the weather, not the calendar. The yucca’s blossoms open in late afternoon exposing the ripe pollen.
After mating, the moth arrives later in the evening, enters the flower, and collects pollen from the ends of the stamens, the male part of the flower. Yuccas are self-fertile — they can seed from their own pollen – so she methodically rolls the pollen into a sticky little ball and lugs it over to the pistil, the female part of the flower that sits on top of the ovary. She pushes the ball up to the top of the pistol, to the stamen, where she vigorously hammers the pollen onto the tip. Following her pollination chore, she lays her eggs in the small, green ovary inside the flower.
As the yucca fruit grows, it develops an encapsulating seedpod, which protects the moth’s larvae. After the larvae hatch into tiny caterpillars, they exuberantly feed on the yucca’s seeds, eventually chewing their way through the seedpod and dropping to the ground where they begin the next step of their life. Since there are plenty of seeds there are always enough left for the yucca to disperse in late summer, assuring the continuation of the species.
Neither the moth nor the yucca could exist without the other. The best time to see the moths in action is at dusk. Look for the creamy blooms of a flowering yucca and bring a flashlight.