When I first saw her dive into the brilliant orange nasturtium I stopped dead in my tracks – I was so fascinated by the speed of her flight, her ability to hover just in front of the flower, as if making up her mind to re- enter that blossom or move on. The pale pink brushed across her speckled/striped mole brown/buff thorax almost seemed like it had been added as an afterthought.
What a magnificent creature I thought, as I remembered the night in June when one had spent the night on porch screen door. I suddenly realized that this was probably when she laid her eggs on the Datura plant I was growing in a pot nearby, because hawk moths loved these plants with their huge lace edged trumpeted flowers. The two had a special relationship. The hawk moth deposited her eggs on the underside of the gray green leaves and pollinated the flower in return. However, once the brilliant lime green tomato hornworm ( larva stage) actually appeared with his solitary horn I was shocked by his eating habits. My beautiful Datura had lost new buds and leaves – they vanished in one night. When I attempted to remove this intruder he hung on so tightly to the branch he was ingesting that it came off with him!
On closer inspection I discovered 6 more of these mighty leaf eaters crawling and munching away on the underside of half eaten leaves. They varied in size from about an inch to almost four inches – the latter could pass for a true monster. This guy had probably been eating for days. What was baffling to me was why this plant had been chosen as the host, while another Datura, one just below the porch was totally ignored. I guess there is no accounting for a hawk moth caterpillar’s taste!
Now every morning I go out and inspect my damaged plant for more leaf tyrants, and this morning found another after a few days reprieve. In spite of extensive defoliation the Datura is making a slow come back, although I think her days of multiple blossoming are over. Prickly round sage seed-pods are developing under the leaves. I don’t mind that this plant’s flowering has been cut short because although I have read about the relationship between the hawk moth/tomato hornworm and Datura, this is the first time I have been able to witness first hand what happens when a Datura is “chosen” as a host.
I understand why the hawk moth is often confused with a hummingbird; the two use similar tactics to gather nectar and behave in similar ways. At first glance it would be easy to mistake one for the other.
These moths overwinter in the soil as dark brown pupae, then emerge and mate in late spring. They lay their eggs, which are round and greenish-white, on the undersides of leaves usually in June. Next year I will be on the lookout for the Datura I plant on my porch!
Some of the largest moths in the world belong to the hawk moth family (Lepidoptera). These magnificent creatures have long narrow wings and thick bodies. They are swift and graceful flyers, highly aerobatic. Many species can hover in place as the one did in front of my nasturtium blossom. Some can briefly fly backwards or dart away. Hawk moths are experts at finding fragrant flowers after dark. They are especially fond of Datura, primroses (they are the primary pollinator of this family which explains why the flowers are so luminous before dawn), orchids, petunias and other flowers with long floral tubes concealing pools of thin but abundant nectar.
Hawk moths have the world’s longest tongues of any other moth or butterfly (some up to 14 inches long). Charles Darwin knew of the star orchids (Angraecum spp.) from Madagascar that had nectar spurs over a foot in length. Darwin was ridiculed by other scientists of his day for predicting that star orchids would be pollinated by these particular moths. After his death, hawk moths with tongues long enough to sip of the nectar produced by the star orchids were discovered on the island of Madagascar. Curiously, some hawk moths are nocturnal and others feed during the day. The ones I have here are abundant day feeders.
Hawk moths have three spectral receptors that are sensitive to blue, green, and ultraviolet light. It was originally assumed that hawk moths relied primarily on olfactory cues to locate flowers, but recent studies have shown that they actually have excellent vision overall.
With a wide geographic range throughout Canada, North, Central, Mexico, South America, Eurasia, and Africa, hawk moths feed on many different host plants as caterpillars and pollinate a variety of flowers. They use both visual and olfactory perception to locate plants from which they collect nectar. They seem to thrive almost anywhere (!) in rural areas, suburbs, mountains and deserts.
If you want to attract these marvelous creatures plant penstemon, red salvia, nasturtiums, and scatter Datura seeds around your property. I promise, you will not be disappointed. But beware of of half eaten leaves with holes!
Postscript: I regularly write a couple of weekly/bi weekly nature columns for publication and some of these end up on my blog because I am so fascinated by the information and don’t want it to disappear into the thousands of writings stored in my computer! I have written a few articles about Datura for this blog because the shapeshifting qualities of this plant amaze me and learning first hand how one can be decimated by the hawk moth larva is yet another source of fascination.