Friday, September 9, 2011


Our friend John Roser, in his nightly patrols to see what's happening in his yard, discovered that giant Five-spotted Hawkmoths are visiting his massive flowering Datura. Since that discovery, several folks have held nightly vigils in John's yard, starting at dusk, to witness the show.

Sacred Datura unfurls its flowers each night. (Photos by Narca)

The Five-spotteds are very large hawkmoths, impressively bigger than the White-lined Hawkmoths that we frequently see here in the Chiricahua Mountains. They appear at dusk or shortly after, zeroing in on the opening white trumpets of Sacred Datura (Datura wrightii). Datura flowers grow up to 8 inches long, of a size to match the huge hawkmoths that they attract.

A Five-spotted Hawkmoth approaches a Datura flower. If you look carefully, you can see its proboscis beginning to probe the lower flower.

As the moth approaches a flower, it extends its extremely long proboscis into the bloom, then dives right in, wriggling past the pollen-bearing stamens into the flower's interior. There it turns around after a few moments and emerges, no doubt well-dusted in new pollen, which it carries to another flower.

The hawkmoth maneuvers into position, its proboscis now deep inside the flower.

Datura is in the plant family Solanaceae, and the big hawkmoth seems perfectly adapted to be its pollinator. The moth's larval food, likewise, is solanaceous plants. So here we have a good example of symbiosis or mutualism––the plant feeds the caterpillar, and when the caterpillar transforms into a giant adult, it insures the survival of the Datura by pollinating the flowers so that they can set seed.

In we go!

The Datura-diving moth quickly enters the flower and vanishes from sight.

The work of several major scientists has led to our better understanding the mutualism that binds flowers and their pollinators. Let's start with Darwin, who put forth the view that evolution (= change over time in the traits inherited by organisms) is driven by competition. However, in the view of Lynn Margulis, cooperation and mutual dependence play an even greater role. Dan Janzen focused closely on the theory of coevolution between flowering plants and their insect symbionts, based on the remarkable specializations shown by an Acacia and an ant, Pseudomyrmex ferruginea; he won the Crafoord Prize for his work in coevolutionary ecology. If the subject of pollination interests you, check out their work, as well as Gary Nabhan's book, The Forgotten Pollinators.

Yes, in the caterpillar stage these beasts are the infamous Tomato Hornworms. Since tomatoes and potatoes are also in the family Solanaceae, they fit the bill for caterpillar food quite nicely. Gardeners sometimes plant marigolds near their tomatoes to discourage the hornworms' interest.

Datura's common name, Sacred Datura, comes from its early ritual use by Native Americans. It is hallucinogenic, but a very dangerous hallucinogen. Adolescents who used the substance in initiation rites regularly died. The plant's compounds can take away vision, depress breathing, cause seizures, and bring on very high fever. Leave it to the hawkmoths!

1 comment:

  1. I just love your blog, found it while the HS2 fire was going!
    Here in Pearce, there are large moths that visit almost nightly, but they don't look as fancy as these I don't think! They are so large that they remind me of hummingbirds.