The Least Among Us: The Story of the Yucca Moth

The sun-baked soil, dusty shrubs of buckwheat and towering stands of yucca in Big Tujunga Canyon have a fragrance all their own. The sound of insects swells and fades; swells and fades... A memory of water lines the dry riverbeds with bits of forgotten froth and algae dried into streaks on marbled granite walls. There is no such thing as silence here where hawks scream inquiry and bees sound like small farming implements: gathering the harvest. 

Photos of Yucca whipplei (and Eva Lund) in Big Tujunga Canyon by Debra McConville


Here in this world just outside the polluted and impersonal city limits, a miracle takes place, a relationship forged in perpetuity ensures the perfect survival of two species and the pleasure of all who appreciate the miraculous.

Standing upright in confident spears, the yucca, or “Our Lord’s Candle” balances the native California landscape of soft mounding shrubs of buckwheat, manzanitas, coyote bush and sage with its vertical 10’ blooms rising from striking rounds of spiked foliage. This plant species has a story to tell about survival and perfect planning. Its presence in this chaparral is no accident; nature abhors such things so every detail of this wild land is deliberate, and none is more so than that of the yucca.

This stately plant owes its entire existence to one small inconspicuous insect: the yucca moth. And the moth in turn would perish forever without the relationship it has forged with the yucca. In the absence of either one of these species, the other would quickly become extinct.

This small white moth is unique in the insect world: her mouth has a pair of spiny tentacles and her egg-laying tube is a sharp spike. One evening in early summer the moths emerge from their cocoons and mate just as the yucca begins to bloom. When the female is ready to deposit her eggs she does the most remarkable thing: this tiny moth enters flower after flower of the majestic yucca and gathers pollen from each in her tentacles. She rolls this pollen into a ball bigger than her head. Then she flies to another flower, inserts her sharp egg-laying tube into the flower’s ovary at the base of the pistil and lays just three eggs. She climbs the pistil and inserts the ball of pollen, rubbing it into the pistil and pollinates the yucca flower. The pollen is neither food for herself or her eggs, this action only benefits the yucca.

Once the flower's ovary is fertilized it swells with hundreds of seeds. The yucca moths' young eat just a few seeds which is why so few are laid in each bloom. Then each little larvae bores a hole in the flower pod, emerges and drops slowly to the ground on a silken thread. It pupates in the ground at the base of the Yucca plant over the winter and leaves its cocoon the following year to start the cycle over again.

In her remarkable book “The Clover and the Bee” Anne Ophelia Dowden writes, “This little moth directly arranges the fertilization necessary to produce seeds her offspring need to eat. In the whole field of pollination it is the only case where an insect ‘deliberately’ fertilizes a flower for the good of the plant and the future benefit of babies she will never see, and is not an accidental part of food gathering.” The yucca moth never eats during her short lifespan. Dowden continues, “No one knows what started such a habit or how the moth’s curious body developed. But the partnership must be very old, since species of yucca have evolved and each has a species of Tegeticula moth that evolved with it. The yucca depends entirely on its little moth.”

This year in the canyon, plant rustlers chopped hundreds of blooming yucca ‘trees’ down and stole them. I believe they were gathering the fertilized seed. The real crime is they stole the yucca moth larvae before they could complete their generous cycle. There will be fewer yuccas next year not only because these plant thieves stole thousands of seeds but because they destroyed so many of the yucca’s only pollinator.

Nature is in perfect balance. When man disrupts it, even in a 'small' way: the balance is upset in ever expanding measures. The loss of a small insect and the plant whose life it ensures can change a whole landscape and the habitat of hundreds of species. Ecology is an exact science whose members (including man) occupy space and coexist in perfect union.

It amazes me that a tiny little life like the yucca moth can think ahead to a future she will never see, yet human beings cannot.