Monday, January 7, 2013

Hawk Moth

I received this picture from fellow Master Naturalist, Michael Baird with a note:
"Here is the Pink-Spotted Hawk Moth, Agrius cingulatus (Fabricius), I found outside of Maschinos, laying in the alley. After doing a little research I found that they are common to Missouri in the fall, occasionally breeding in southern counties.  The adults visit flowers, usually the deep-throated species."
Butterflies and Moths of Missouri* has this to say about A. cingulatus: "In Missouri, there are records from June to mid-November."

by Paul Ingram on
As Michael notes, "Adults nectar from deep-throated flowers including moonflower (Calonyction aculeatum), morning glory (Convolvulus), honey suckle (Lonicera) and petunia (Petunia species)."**  It feeds by hovering like a hummingbird while unrolling its incredibly long proboscis into the deep well of nectar.

The Agrius cingulatus (a.k.a. Sweet Potato Hornworm) larva is shaped like a typical hornworm (think Tomato Hornworm) but with different coloration and vertical stripes on its head.  Like other hornworm caterpillars, it shares a digestive affinity for the same vegetable plants that we do, in this case eating the leaves of a tuber, the sweet potato.  Some would call this a pest, others a beauty.

Originally it was a neotropical species with a range from South America and Mexico with some migrating as far north as Canada.  Since then A. cingulatus has really taken advantage of the Columbian Exchange and become a world traveler as in this early report:  "Specimens have been found in England (Barrett, 1895) and on ships off the French coast."  Now it really gets around.

"Extra-limital range: The tropics and subtropics of the New World, and the Galapagos and Hawaiian Islands. As a migrant, Agrius cingulata flies north to Canada, south to Patagonia and the Falkland Islands and, occasionally, to western Europe. A. cingulata has recently established itself in the Cape Verde Islands west of Senegal, West Africa (Bauer & Traub, 1980), adults having arrived, presumably, from Brazil."

So what is the secret of its successful travel around the world?  I speculate that like Popeye, it is in what A. cingulatus larvae eat.  The favorite food of its larvae is the sweet potato, Ipomoea batatas.  Unlike Popeye, who said "I yam what I yam and that's all that I yam," the sweet potato is not a true yam but a member of the morning glory family, producing the same deep flowers that the moth likes to nectar upon.

Originating in the Western Hemisphere, the sweet potato has been spread around the world by man.  It is propagated by vine cuttings and not by seeds.  It first traveled to central Polynesia around 700 AD, possibly transported by Polynesians who some feel reached South America around that time.***  Following the Columbian Exchange created by early European exploration of South America, it traveled to Africa where the sweet potato became a popular staple.  Transported by cuttings, I would speculate that the A. cingulatus larvae  and eggs also made the trip on the vines necessary to survive the long ocean voyage.

*       Butterflies and Moths of MissouriJ. Richard and Joan E. Heitzman.
**     This quote and a picture of its incredible proboscis is from
***   For more on this see Sweet_potato 

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