Yucca Moth

(Tegeticula yuccasella )
also commonly called the pronuba mot

The Yucca Moth

The Yucca Moth, emerging from her cocoon, flies at night to a Yucca flower and collects pollen from the stamens, holding a little ball of it in her mouth-parts. She then visits another flower and lays an egg in the seed-box. After this she applies the pollen to the tip of the pistil, thus securing the fertilisation of the flower and the growth of the ovules in the pod. Yucca flowers in Britain do not produce seeds because there are no Yucca Moths.
Date: 1922. Author : J. Arthur Thomson

The yucca moth, also commonly called the pronuba moth, is a small white moth that lives in the semi-arid habitats where yucca plants grow. The yucca moth is well-known for its co-dependant relationship with the yucca plant. The yucca moth’s larvae rely exclusively on the seeds of the yucca plant as a primary food source, and the plant relies exclusively on the yucca moth for pollination. One cannot exist without the other, creating an obligate mutualism between the moth and the plant. This is true of two out of the three genera of yucca moths, the Tegeticula and Parategeticula.

Range

Conforms to its yucca plant species host's range (which may vary from region to region). The yucca moth is native to the southwestern United States and Mexico. The Sonoran Desert region is home to approximately ten species of yucca plant, and where there are yucca plants, there are yucca moths. Yucca moths are also found in the southeastern portion of the U.S. and the West Indies, where just one species of yucca plant is known to exist.

Cluster of soaptree yuccas (Yucca elata)

Taxonomy

Belongs to the order of Lepidoptera, insects with four wings covered with minute scales; order includes moths, butterflies and skippers. There are approximately 80 species of Prodoxidae.

Class -- Insecta
Superorder -- Amphiesmenoptera
Order -- Lepidoptera
Suborder -- Glossata
Infraorder -- Heteroneura
Superfamily -- Incurvarioidea
Family -- Prodoxidae

Overall Anatomy

The yucca moth is silvery, white and small in size.

In the course of its evolution, the Yucca Moth has developed specialized mouth organs that it uses to collect the yucca's pollen, packing and transporting the tacky substance under its head (or "chin").

body length of roughly less than an inch
wing span of about an inch
females are slightly larger than males
whitish forewings with white hair-like fringes in most species, some with dark markings; dark wing color in some species
grayish brown hindwings with white hair-like fringes
white head and thorax (the body's second, or midsection);
brownish abdomen (the body's third section)
yellowish legs
antennae

Behavior

In the spring, the yucca moths emerge from their subterranean cocoons and are lured by the fragrance of the blooms on the nearby yucca plants. The yucca moths spend most of their time perched on or near yucca plants. If the moths are not resting, they are flying from plant to plant, collecting pollen, pollinating, mating or laying eggs.

The Yucca Moth

If you want to observe a yucca moth in action, find a yucca plant in bloom. The yucca moth usually rests on the yucca plant or bloom during the day and pollinates and lays eggs at night when the blooms are fully open.

Reproduction and Life Cycle of the Yucca Moth

Male and female Tegeticula yuccasella moths use the yucca blooms as a bridal chamber, with the male abdicating all responsibility for the female and the larvae after mating. Mating occurs in the evening hours when the yucca blooms are fully open.

When the yucca plant begins its spring bloom, signaling its readiness for pollination, the yucca moth, using her specialized mouth organs, collects the highly adhesive pollen from the yucca flowers' male sex organs, or anthers. Typically secretive - the female yucca moth works only in the darkness between sunset and midnight - and choosy - she seeks the newest of blooms - the yucca moth, once pollen laden, now enters a flower and circles and evaluates the female reproductive organ, or ovary. She may withdraw and renew her search if she finds that another yucca moth has visited the flower ahead of her. Once she makes a choice, she lays eggs in a specific location within the flower's ovary. She then climbs the ovary's stigma and deposits a small fragment of her pollen, fertilizing the flower so that it soon begins producing fruit and the seeds for her coming offspring. With only a few days left in her lifetime, she soon moves on, searching for another acceptable bloom.

The yucca moth’s larvae hatch within several days, with the yucca plant - keeping its end of the bargain - providing its fruit for housing and some seed for food. When conditions are right, ideally soon after a nighttime thunderstorm, the yucca moth larvae leave the fruit of the yucca and drop to the desert soil. They burrow down one to three inches. Each creates a cocoon, where it may develop for several weeks to several years before it emerges to renew the cycle.

Interesting Facts About The Yucca Moth

The female yucca moth collects pollen, forming a compact ball that is three times the size of her head which she transports to other yucca flowers
The yucca moth is one of the oldest moth species
Yucca plants would not exist without the yucca moth and vice versa

The Yucca Moth and the Yucca Plant

Even though they belong to two different kingdoms in the universe of life on our planet, the yucca moth species known as "Tegeticula yuccasella" and the yucca plant species known, popularly, as the "soaptree yucca" and, scientifically, as the "Yucca elata" have forged an inseparable bond. They co-evolved over millions of years, and maintain a mutual dependence. Although dozens of other yucca moth and yucca plant species have similar relationships, the Tegeticula yuccasella and Yucca elata, in the United States' desert Southwest, stand as a classic example of the biological phenomena known as "coevolution" and "mutualism."

Watch a video about the Joshua Tree (Yucca brevifolia).

In their biological partnership, the moth depends on the fruit of the yucca for the developing seeds that serve as the sole source of food for its larvae. Conversely, the yucca depends on the females of the moth species for the pollination of its flowers and the consequent production of fruit and seeds. Without the Yucca elata, the Tegeticula yuccasella would perish with the last of the existing generation. Without the moth, the yucca would expire with the end of the existing stands. (The yucca can sprout new plants from its roots, but it cannot readily expand a range or establish new ranges to form new stands without the more mobile seeds.)