Scalpel in hand, Dr. Marcia Loeb slices into the insect under her microscope and extracts a pea-sized organ she thinks may hold the key to saving millions of acres of trees in the United States.
It is the reproductive organ of the male gypsy moth, one of the most destructive pests in the country. If she can thoroughly understand its reproductive system, she might be able to find a poison that would halt the spread of the insect and the damage it causes.
As a research physiologist at the federal Beltsville Agricultural Research Center, Loeb has spent 18 years cutting open the little creatures and examining their organs. She is one of the few researchers in the country delving into the male moth's reproductive system, an area of study she considers a necessity.
"There's been very little work on males, and yet it's obvious that ++ it takes two to tango," said Loeb, 63, of Bethesda.
She is credited with helping to discover that male gypsy moths, like human males, have a protein in their brains that turns on the production of steroids, which trigger the growth and development of the reproductive system.
"She's done some outstanding work in a field where there isn't a lot of glory attached," said Terrance Adams, a researcher who focuses on female gypsy moths at a U.S. Department of Agriculture laboratory in Fargo, N.D.
Scientists have been studying Lymantria dispar for decades, and many are convinced that the key to controlling it might be in stifling its reproductive abilities.
But they still are puzzled by how the gypsy moth's reproductive system develops and how the moths can spawn hundreds of offspring in the few weeks that they survive as adults.
Loeb said it might be years before she and other scientists can answer such questions. But there is one obvious clue.
"They're really very promiscuous," she said of the gypsy moths.
Loeb's work involves research, writing and -- in a lab where a brightly colored, photo of a menacing gypsy moth decorates the door -- dissecting moths about every two weeks.
She begins by washing the insects in detergent and household bleach. She then places them on a brightly lighted slide and slices into them to extract their testicles.
Stretched out on a dish, under the glare of Loeb's microscope light, the gypsy moth gives off a silvery sheen that makes it look like the metallic band of a woman's wristwatch.
"They really are kind of an attractive animal," Loeb said as she peered through the eyepiece.
They might be "attractive," but gypsy moths have caused their share of damage since they were shipped to Medford, Mass., in 1869 by a French scientist hoping to crossbreed them for silk production.
In 1981, gypsy moths defoliated 13 million acres of trees in the United States. In 1990, they destroyed 133,062 acres of trees in Maryland, said Mark Taylor, coordinator of the gypsy moth suppression program for the state Department of Agriculture.
"The problem is that they don't really have natural predators in the U.S.," Taylor said.
The sharp, pointed "spines" along their sides make gypsy moths unpalatable for birds, scientists say. The identity of the predator that keeps them in check in Europe remains a mystery.
"All they do is grow, eat and reproduce," said Loeb, who has studied insects since childhood, when she began collecting caterpillars while on walks with her father, a high school science teacher in the Bronx, in New York City.
"We'd take them home and see if they would hatch. As a child, I remember thinking how fascinating that was," she said.
Loeb earned a bachelor's degree in biology from Brooklyn College in 1953, a master's degree in zoology at Cornell University in 1957 and a doctorate in physiology from the University of Maryland in 1970.
She came to Beltsville in 1978 and began studying gypsy moths, which, like butterflies, begin as eggs, then go through the caterpillar and pupa stages before becoming adults.
Loeb also is studying the intestine of the tobacco budworm, a pest known to have wiped out a California lettuce crop and cotton crops across the South.
From the budworm, she extracts the tiny intestine, which looks like a sliver to the naked eye.
Sprays and insecticides are available to combat gypsy moths and budworms, but they pose hazards to other insects and wildlife, experts say. Loeb's work could lead to a better understanding of pests and the development of insecticides and other agents to kill them safely.
"You need to have a basic understanding of how an insect works to come up with some control of them," said Dr. Raziel S. Hakim, a researcher and anatomy professor at the Howard University Medical School in Washington. "That basic understanding is what her work is all about."
Pub Date: 1/04/97