It May Be Elusive but Moth With 15-Inch Tongue Should Be Out There
By NATALIE ANGIER
Published: January 14, 1992
IT may never have been seen by human eyes, and it certainly has never been described in the scientific literature, but somewhere in the dense tropical highlands of Madagascar there must flutter a moth with a tongue that measures 15 inches in length, a scientist says.
Speaking recently at an entomology meeting in Reno, Nev., Dr. Gene Kritsky of the College of Mount St. Joseph in Ohio said that there was no alternative but to posit the existence of a giant moth with a six-inch wingspan and a longer proboscis than any yet seen on an insect. He made his prediction based on the existence of a rare orchid in Madagascar, a flower that could only be pollinated by a moth able to stick its tongue way down a tube where a pool of tempting nectar is hidden.
The tube of the exotic bloom, called Angraecum longicalcar, is 16 inches deep, and it hangs down from the blossom's stem like a whip; the nectar fills up about an inch on the bottom. Thus, said Dr. Kritsky, a moth would need to uncoil its proboscis to 15 inches to reach into the tube, called a nectary, suck up the juice and incidentally detach the orchid's pollen packet at the same time. Dr. Kritsky believes that the pollinating moth is a member of the sphinx moth family, and that it would be found if a diligent scientist willing to brave Madagascar's political chaos were to search for it. Taking a Cue From Darwin
"The orchid and its pollinator must have co-evolved," said Dr. Kritsky. "The orchid could only survive if it had a moth pollinator."
The entomologist said he was doing nothing more than taking his cue from Charles Darwin, the great naturalist and occasional soothsayer. In 1862, while studying a Madagascan orchid, Angraecum sesquipedale, Darwin proposed that there must be a moth with an 11-inch tongue, able to dip into the flower's foot-long nectary and pollinate it. In 1903, two entomologists discovered a sphinx moth in Madagascar with a proboscis that matched Darwin's prophecy.
While rummaging through a natural history library last spring, Dr. Kritsky came upon a description of an orchid with an even longer nectary, and he decided it must have a pollinator with an even lengthier tongue. Other entomologists who heard his presentation agreed.
"It seems highly likely that another species of moth with a slightly longer proboscis is out there, able to pollinate that orchid," said Dr. Nathan M. Schiff, a research entomologist with ARSB Research Laboratory in Beltsville, Md., a Government agency. "Darwin got it right, and Gene Kritsky is just following in his footsteps."
Dr. Kritsky said that the orchid and its fertilizing insect probably evolved together over time, with the nectary getting a bit longer, and the moth's tongue following suit, until the relationship between the two became exclusive, a type of interdependence that suited both: the moth, because it could always be assured of a nectar drink from the orchid, which no other insect could penetrate; and the flower, because it could guarantee that its pollinator would be focusing its efforts on longicalcar and therefore would be likely to deliver fertilizing pollen from one bloom to another. Projections Trap Insects
Dr. Kritsky said that the orchid discouraged small, scavenging insects like ants from crawling down its tube to gorge on its precious nectar with fingerlike projections along its nectary lining that trap the insects.
To retrieve nectar from the flower, he said, a sphinx moth would have to settle on a lip at the edge of the skinny tube, and carefully uncoil its proboscis. As the moth probed, a pollen packet would shake loose from the orchid and stick to the moth. When the insect flew to another orchid, the packet would become detached and fertilize the recipient flower.
Dr. Kritsky said he has never seen the longicalcar orchid himself, but that the Cincinnati Museum of Natural History, where he works as an adjunct curator, is trying to get a sample. As for its fertilizing moth, because the insect is likely to be nocturnal, and because it must live in a remote region of the Madagascan jungle, where the longicalcar orchid blooms, it may never have been seen by a human being.
"Nathan Schiff told me I had to go find this thing," said Dr. Kritsky. "He said if I didn't, he would do it himself."
Diagram: "Portrait of an Unseen Insect" The existence of a rare orchid with a 16-inch-deep nectar tube has led to the hypothesis that a giant Madagascar moth with a 6-inch wingspan and a 15-inch proboscis must also exist. Above, an artist's version of the only creature that could pollinate the orchid, with its tongue uncoiled.