Research Entomologist Robert Whitcomb

Robert Franklin Whitcomb, 75, a research entomologist at the Beltsville Agricultural Research Center who identified more than 50 new species of leafhoppers and about 60 new species of microorganisms, died of brain cancer Dec. 21 at Hacienda Rehabilitation and Care Center in Sierra Vista, Ariz. He lived in Sonoita, Ariz.

Dr. Whitcomb was known worldwide for his 1972 discovery of the genus Spiroplasma, a group of mollicutes, or small bacteria without cell walls. He worked on these microorganisms for the rest of his career.

"The world is essentially a microbial world," he wrote in a 1989 paper. "Although we may pretend to be eukaryotes, we are impostors. . . . Spiroplasma, although discovered a mere 17 years ago, may be the largest genus of any kind on earth and may contain more than a million species."

He also was deeply interested in birds, and one of his articles, which applied the ideas of island biogeography to mainland bird populations in the eastern deciduous forest, was considered a landmark study. It led to the current emphasis on the negative effects of forest fragmentation on biota, or all the living organisms of the forest.

On the Agriculture Department's Beltsville campus, Dr. Whitcomb was widely credited with the successful re-creation of its grasslands, a unique landscape in the Washington area that contains the progeny of plants seeded in Colonial times or before. More than 234 species live in the uncut meadowland, he told a Washington Post reporter in 1997, and it's managed naturally. Ideally, that would include lightning-set fires.

"I called the Prince George's Fire Department and asked what would happen if I set a match. [A fire official] said, 'You can set fire, but I've got to come and put it out,' " Dr. Whitcomb said. "I don't think our director would be too happy if we burned down the surrounding subdivisions, but I'd love to torch the savanna."

The savanna is off Poultry Road, near a row of houses just beyond the 7,000-acre government farm. "These people were complaining because of a wasp nest in our trees," Dr. Whitcomb told The Post. "Can you imagine what would happen if we torched the prairie?"

Few might expect a natural scientist to be born in New York City, as Dr. Whitcomb was. He graduated from Blackburn College in Carlinville, Ill., and received a master's degree in entomology in 1958 and a doctorate in plant pathology in 1961, both from the University of Illinois. He did postdoctoral work in entomology at the University of California at Berkeley for five years. He moved to the Washington area in 1966 to work at Beltsville, where he remained for the next 30 years.

He was an original member of the International Organization for Mycoplasmology in 1974 and taught one of its methods courses in Bordeaux, France, in 1984. He received the group's highest honor, the Kleineberger-Nobel award, in 1994. He published more than 300 scientific papers and in 1979 was one of four editors of a new series of scientific reference books, "The Mycoplasmas."

Dr. Whitcomb, who also had a home near Elkins, W.Va., enjoyed participating in the Christmas Bird Counts in the Washington area from 1970 through 1996. He moved to Arizona the next year and participated in the counts there as well. He ran surveys on several breeding bird routes in West Virginia for more than 30 years, and in 1988, he coordinated the northeastern quarter of the West Virginia Breeding Bird Atlas.

In retirement, he became interested in oral history and recorded interviews with members of the World War II generation, some of which were turned into articles in the West Virginia magazine Goldenseal.

Dr. Whitcomb also published two books of his poetry, in 1998 and 2007, and was a member of an Arizona poetry group. He played competitive Scrabble for the past 10 years.

His marriages to Mary Brown and Miriam Becker Courtney ended in divorce.

Survivors include his wife, Judith Whitcomb of Sonoita; four children from his first marriage, Bruce Whitcomb and Julie Whitcomb Yates, both of Baltimore, and Douglas Whitcomb and Stephen Whitcomb, both of Columbia; two stepdaughters, Pam Olejar and Ruth Courtney, both of Fort Lauderdale; and five grandchildren.