How does this blue-blood turn green?
By Chelsie Vandaveer
August 21, 2002
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
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The tobacco hornworm or hawkmoth (Manduca sexta Linnaeus) is a member of the Sphingidae or sphinx moth family. These night-flying moths are frequently mistaken for hummingbirds; they generally hover while feeding at fragrant night-blooming flowers. But they have been observed landing in the floral tube of large flowers like angel's trumpet. Angel's trumpet nectar is toxic and the hawkmoth appears to 'enjoy' the brew.
The caterpillar feeds preferentially on tobacco (Nicotiana spp. Linnaeus). The hornworm's 'blood' contains a blue protein, insecticyanin. When the caterpillar feeds on tobacco, it ingests carotenoids. The yellow carotenoids bind to the insecticyanin providing the hornworm with green camouflage. Caterpillars fed on diets without the carotenoids are blue.
The nicotine in tobacco is toxic to most insects. The tobacco hornworm sequesters the nicotine and secretes it as a regurgitant. The regurgitant rids the hornworm of the toxin and serves as a deterrent to predators. The caterpillar will 'spit-up' the foul brown liquid on any disturbing creature including gardeners attempting to remove them from flowering tobacco (Nicotiana alata Link & Otto).
The regurgitant, though, does not completely work in the hornworm's favor. In "Molecular Interactions between the Specialist Herbivore Manduca sexta and Its Natural Host Nicotiana attenuata" (Plant Physiology, Feb. 2001), Halitschke, et al, found that the regurgitant on wounded (caterpillar chewed) leaves provokes a response from the plant. The plant releases terpenes and ethylene gas. This does not affect the hornworms, but appears to attract the attention of parasitoids which lay their eggs on the backs of the caterpillars.
The Northern Prairie Wildlife Research Center of the USGS has photographs of the tobacco hornworm and the hawkmoth. To view the photographs, click on the link:
http://www.npwrc.usgs.gov/resource/distr/lepid/moths/az/1081.htm
The Institute of Food and Agricultural Services, University of Florida has a photograph of a hornworm parasitized with the eggs of a wasp taken by James Castner. To view the photograph, click on the link:
http://creatures.ifas.ufl.edu/field/wasp_pupae.htm
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
Suggested Reading:
What is the hickory horned devil? Renfield's Garden - June 4, 2003
What moth has feathers? Renfield's Garden - July 3, 2002
How does this blue-blood turn green? Renfield's Garden - August 21, 2002
What moth makes insect repellant? Renfield's Garden - August 28, 2002
What experiment turned into a yearly disaster? Plants that Changed History - December 25, 2001
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Michigan Bulb -$20 off—>Click here.
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Wollemi Pine
National Geographic®
Exclusively from National Geographic, this survivor from the age of the dinosaurs is one of the greatest living fossils discovered in the 20th century. The Wollemi pine is one of the world's oldest and rarest tree species, belonging to a 200-million-year-old plant family thought to have been extinct for more than two million years.
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Previously known only from fossil records, it was presumed extinct until a single tree was found in the Wollemi National Park, Australia, in 1994. Subsequent research discovered 100 adult trees that have survived in a single canyon in this wild and rugged area.
Click here to view canyon, trees and fossil record.
You can assist in the conservation effort and enjoy the unique opportunity to ensure the continued survival of this rare species by giving the tree as a gift or growing your own. Suitable for indoor container gardening or as a landscape tree in certain areas of the U.S.
Comes with a care manual with the full story about the discovery and fascinating history of the Wollemi pine. Comes in a copper-colored container and will be approximately 10''H when shipped. A portion of the proceeds from the sale of these plants will fund ongoing conservation research.
Click here to get your Wollemi Pine and assist in the conservation effort.
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National Geographic Magazine
National Geographic®
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You are invited to roam the world in the pages of National Geographic magazine. Explore the diversity of our planet's lands and inhabitants in compelling stories covering topics such as animals, nature, science, technology, culture, history, travel, adventure, exploration, and geography. The monthly National Geographic magazine is your key benefit of membership.
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Join the Society and bring the adventure of National Geographic into your home!
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