Forbes, Stephen Alfred

(b. Silver Creek, Stephenson County, Illinois, 29 May 1844; d. Urbana, Illinois, 13 March 1930)

biology.

The fifth of the six children of Isaac Forbes and Agnes Van Hoesen, Stephen A. Forbes was raised on a farm in relative poverty. When Stephen was ten, Isaac Forbes died and the elder son, Henry, supported the family. After a year at Beloit Academy, Stephen accompanied Henry into the cavalry on the Union side in the Civil War. Forbes later regarded these years of military service, from September 1861 to November 1865, including four months as a prisoner of war, as a valuable stimulus to his education.

After three years of studying medicine, Forbes decided to study natural history. He supported himself by teaching school in various Illinois towns between 1868 and 1872. Attending the Illinois State Normal University only briefly, Forbes pursued the study of natural history on his own. He married Clara Shaw Gaston in 1873 and had five children. The family was Unitarian, Forbes having moved from the orthodox religion of his childhood to a scientific agnosticism. Throughout his life Forbes was physically and mentally energetic and healthy, enjoying variety in exercise and in reading.

In 1872 he was made curator of the Museum of the State Natural History Society, Normal, Illinois, which he transformed into the Illinois State Laboratory of Natural History in 1877. The laboratory and museum were moved to Urbana when he became a professor at the University of Illinois. This was in 1884, the same year he received his Ph.D. from the University of Indiana. Forbes was appointed state entomologist in 1882. The Office of the Entomologist and the State Laboratory of Natural History were combined when the State Natural History Survey was created. Forbes was chief of the Survey until his death. Forbes’s earliest love had been botany, but his first professional concern was how best to teach natural history in the public schools. He was active in the campaign, led by Louis Agassiz, for laboratory and field work. Forbes’s first major research was a series of studies of the stomach contents of birds and fish that he collected in Illinois. Naturalists had, of course, made scattered notes of what a particular animal was observed to eat, but Forbes undertook a systematic program to determine directly, often by microscopic examination, what foods had been eaten and in what proportion. He became an authority not only on birds and fish but on the insects and crustacea that they ate. Throughout his career he maintained an interest in limnology, establishing a floating laboratory in the Illinois River in 1894. After his appointment as state entomologist in 1882, most of Forbes’s work concerned insects harmful to agriculture. Highly respected in this field, he was president of the American Association of Economic Entomologists in 1893 and 1908, president of the Entomological Society of America in 1912, and elected to the National Academy of Sciences in 1918.

The scientific work of Stephen Alfred Forbes was dominated by his interest in ecology. From the outset he was concerned to investigate scientifically, and quantitatively where possible, the interrelations that make a group of individuals into a functioning system. His viewpoint was clearly and explicitly based upon that of Charles Darwin and Herbert Spencer. He studied the food of fish and birds because he saw the predator-prey relation as the most direct ecological link between species. He expected such studies to help explain not only the geographical distribution and abundance of a species but also its evolution. Forbes found in these studies considerably less specialization than expected, although there were characteristic differences in the proportion of various foodstuffs consumed by each species. The fact that each prey species had many enemies revealed the complexity of the system. Forbes decided that the oscillations in number inherent in a simple predatorprey relation, well described by Spencer (Principles of Biology, II, 399), would be damped when these relations were more complex, and he interpreted lack of specialization as an evolutionary adaptation to avoid harmful oscillations. Forbes also found that structural factors were correlated with feeding habits only in a very general sense. The physical adaptation of predator and prey seemed less exact than Darwinists assumed, while the invisible “psychological” factor of food preference, presumed heritable, responded to natural selection.

Spencer had described the stable balance generally found in nature as the result of a physiological law governing reproductive energies, for he thought natural selection unable to produce the necessary mutual adjustment of reproductive rates. But Forbes suggested that natural selection could act on the predatorprey pair as a unit, requiring them to achieve a profitable adjustment to each other or both lose out in the struggle for existence. These apparent enemies have, he said, a common interest. Forbes believed that in the isolated and constant environment of certain lakes, the assemblage of species was “sensible,” that is, the entire system was sensitive to whatever affects one species; the assemblage is like an organism composed of interdependent organs. In the microcosm of a lake, the entire complex of species had a “community of interest,” so that natural selection would tend to produce maximum productivity and stability of the whole.

Forbes repeated these ideas from his 1880 articles, in a somewhat popularized form, in a lecture read to the Scientific Association of Peoria, Illinois, on 25 February 1887. This lecture, “The Lake as a Microcosm,” was later hailed as a minor classic by ecologists for its early statement of the concept of community. Karl Moebius’ 1877 booklet on oysters (published in English in 1883) has been similarly hailed. The idea Moebius embodied in his definition of biocoenosis was that an area would hold a given sum of life, so that should the number of oysters be reduced, the number of mussels or other species would increase to maintain the sum.

In 1907 Forbes reviewed his data of thirty years of collecting fish, with the idea of analyzing statistically the geographic distribution of different species. The probability of cooccurrence of two species was predicted from their independent frequencies in his collection; comparing this with their actual cooccurrence yielded his so-called coefficient of association. He applied a similar analysis to data collected in a special survey of birds, giving mathematical expressions for the preference of different species for different types of fields. He had wondered in 1878 whether closely related species living together ever completed for the same food; in 1884 he had described how species of insects feeding on the strawberry plant avoid direct competition by separation in time; in 1907 he hoped to use his coefficient of association to uncover “evasions of competition, and the escape from its consequences, by those closely related and similarly endowed...” (“On the Local Distribution of Certain Illinois Fishes,” in Bulletin of the Illinois State Laboratory of Natural History, 7 [1907], 275). Modern ecologists likewise find the competitive exclusion principle a fruitful basis for research.

While his understanding of the “sensibility” of an assemblage led him to warn of unwanted results if farmers and fishermen tried to alter the balance of nature with inadequate knowledge, his view of the flexibility of natural systems made him hopeful that man could learn how to alter the balance in his favor without disaster. For example, beginning in 1882 Forbes studied the natural diseases of insect pests in the hope of controlling them biologically rather than chemically. He interpreted the agricultural problems with which he dealt as state entomologist as a lack of adjustment of plant and insect, characteristic of the first, primitive stage of association, when evolulution had not yet produced mutual adaptation.

In 1859 Darwin had plainly shown not only the possibility of explicitly analyzing the dependencies of organisms but indeed that such an analysis, along with the laws of variation and inheritance, was the key to the origin of species. Yet the existing momentum of academic biology made comparative anatomy, embryology, and paleontology the fields for evolutionary studies, while ecology, like genetics, became well established only in this century. To the modern ecologist Forbes therefore seems remarkably ahead of his time, for he worked on questions not widely appreciated until twenty or thirty years later. What is perhaps more remarkable is that the science of ecology, whose problems and methods had been so clearly defined in the 1880’s, had such a long gestation period.

BIBLIOGRAPHY

I. Original Works. Most of Forbes’s work appeared in the various publications of the Office of the Illinois State Entomologist, the Illinois State Laboratory of Natural History, the Agricultural Experiment Station of the University of Illinois, and the Illinois State Natural History Survey. An extensive bibliography of his scientific articles, compiled by H. C. Oesterling, is given in Biographical Memoirs. National Academy of Sciences, 15 (1934), 26–54.

I have referred particularly to the following: “The Food of Birds,” in Transactions of the Illinois State Horticultural Society, 10 (1877), 37–44; “The Food of Illinois Fishes,” in Bulletin of the Illinois State Laboratory of Natural History, 1 , no. 2 (1878), 71–89; “Studies of the Food of Birds, Insects, and Fishes, Made at the Illinois State Laboratory of Natural History, at Normal, Illinois,” the subtitle given to no. 3 (1880) and no. 6 (1883) of the same journal.

Among his articles on insects affecting the strawberry is “On the Life-histories and Immature Stages of Three Eumolpini,” in Psyche, 4 (1884), 123–140. “The Lake as a Microcosm” was published in the first and only volume of the Bulletin of the Scientific Association of Peoria, Illinois, pp. 77–87, and reprinted in Bulletin of the Illinois State Natural History Survey, 15 (1925), 537–550. “Preliminary Report Upon the Invertebrate Animals Inhabiting Lakes Geneva and Mendota, Wisconsin, With an Account of the Fish Epidemic in Lake Mendota in 1884,” is Bulletin of the United States Fish Commission, 8 (1890), 473–487.

See also “Summer Opening of the Biological Experiment Station of the University of Illinois,” a pamphlet published by the University of Illinois (1896), 24 pp.; “On the Local Distribution of Certain Illinois Fishes: An Essay in Statistical Ecology,” in Bulletin of the Illinois Laboratory of Natural History, 7 (1907), 273–303; “An Ornithological Cross-section of Illinois in Autumn,” ibid., 305–335; and “History of the Former State Natural History Societies of Illinois,” in Science, 26 (1907), 892–898.

The third Report on the Natural History Survey of the State of Illinois (1909) is a monograph by S. A. Forbes and R. E. Richardson entitled The Fishes of Illinois; the 2nd ed. of this book was published in 1920.

Of additional interest are “Aspects of Progress in Economic Entomology,” in Journal of Economic Entomology, 2 (1909), 25–35; “The General Entomological Ecology of the Indian Corn Plant,” in American Naturalist, 43 (1909), 286–301; and “The Ecological Foundations of Applied Entomology,” in Annals of the Entomological Society of America, 8 (1915), 1–19.

A posthumously published autobiographical note, written in 1923, is “Stephen Alfred Forbes,” in Scientific Monthly, 30 (1930), 475–476.

II. Secondary Literature. The fullest account of Forbes is Leland Ossian Howard, in Biographical Memoirs. National Academy of Sciences, 15 (1934), 3–54. This incorporates material from the autobiography cited above, from a memorial pamphlet published by the University of Illinois in 1930, and from an obituary by Henry Baldwin Ward, “Stephen Alfred Forbes—A Tribute,” in Science, n.s. 71 (1930), 378–381.

Mary P. Winsor

Stephen Alfred Forbes (1844 – 1930)
American entomologist and naturalist

Stephen Alfred Forbes, an entomologist and naturalist, was the son of Isaac Sawyer and Agnes (Van Hoesen) Forbes. Forbes was born at Silver Creek, Ill. His father was a farmer, and died when Stephen was 10 years old. An older brother, Henry, then 21 years old, had been independent since he was 14, working his way toward a college education, but on his father's death he abandoned his career, took the burden of his father's family on his shoulders, and supported and educated the children. He taught Stephen to read French, sent him to Beloit to prepare for college; and when the Civil War came he sold the farm and gave the proceeds (after the mortgage was paid) to his mother and sister for their support. Both brothers then joined the 7th Illinois Cavalry, Henry having retained enough money to buy horses for both. Stephen, enlisting at 17, was rapidly promoted, and at 20 became a captain in the regiment of which his brother ultimately became colonel. In 1862, while carrying dispatches, he was captured and held in a Confederate prison for four months. After liberation and three months in the hospital recuperating, he rejoined his regiment and served until the end of the war. He had learned to read Italian and Spanish in addition to French, before the war, and studied Greek while in prison.

He was a born naturalist. His farm life as a boy and his open-air life in the army intensified his interest in nature . After the close of the war, he began at once the study of medicine, entering the Rush Medical College where he nearly completed the course. His biographers have not as yet given the reason for the radical change in his plans which caused him to abandon medicine at this late stage in his education; but the writer has been told by his son, that it was "because of a series of incidents having to do mainly with operations without the use of anesthetics which convinced him that he was not temperamentally adapted to medical practice." His scientific interests, however, had been thoroughly aroused, and for several years while he taught school in southern Illinois, he carried on studies in natural history. In 1872 through the interest and influence of Dr. George Vasey, the well-known botanist, he was made curator of the Museum of State Natural History at Normal, Ill., and three years later was made instructor in zoology at the normal school. In 1877 the Illinois State Museum was established at Springfield; and the museum at Normal, becoming the property of the state, was made the Illinois State Laboratory of Natural History. Forbes was made its director. During these years he had been publishing the results of his researches rather extensively, and had gone into a most interesting and important line of investigation, namely the food of birds and fishes. He studied intensively the food of the different species of fish inhabiting Illinois waters and the food of the different birds. This study, of course, kept him close to entomology, and in 1884 he was appointed professor of zoology and entomology in the University of Illinois. The State Laboratory of Natural History was transferred to the university and in 1917 was renamed the Illinois Natural History Survey. He retained his position as chief, and held it up to the time of his death. He was appointed state entomologist in 1882 and served until 1917, when the position was merged in the survey. He retired from his teaching position as an emeritus professor in 1921. He served as dean of the College of Science of the university from 1888 to 1905.

All through his career Forbes had been publishing his writings actively. As early as 1895, Samuel Henshaw, in his Bibliography of the more Important Contributions to American Economic Entomology, listed 101 titles. It is said that his bibliography runs to more than 500 titles. And the range of these titles is extraordinary; they include papers on entomology, ornithology, limnology , ichthyology, ecology , and other phases of biology. All of his work was characterized by remarkable originality and depth of thought. Forbes was the first writer and teacher in America to stress the study of ecology, and thus began a movement which has gained great headway. He published 18 annual entomological reports, all of which have been models. He was the first and leading worker in America on hydrobiology. He studied the fresh-water organisms of the inland waters and was the first scientist to write on the fauna of the Great Lakes . His work on the food of fishes was pioneer work and has been of very great practical value. Forbes was a charter member of the American Association of Economic Entomologists and served twice as its president. He was also a charter member of the Illinois Academy of Science; a member of the National Academy of Sciences and of the American Philosophical Society; and in 1928 was made an honorary member of the Fourth International Congress of Entomology. Indiana University gave him the degree of Ph.D., in 1884, on examination and presentation of a thesis. He married, on December 25, 1873, Clara Shaw Gaston, whose death preceded his by only six months. A son, Dr. Ernest B. Forbes of State College, Pa., and three daughters survived him.

[Leland Ossian Howard ]

RESOURCES

BOOKS

Croker, Robert A. Stephen Forbes and the Rise of American Ecology. Washington, DC: Smithsonian Institution Press, 2001.

PERIODICALS

Dictionary of American Biography. Base set. American Council of Learned Societies, 1928–1936. Reproduced in Biography Resource Center. Farmington Hills, MI: The Gale Group. 2002.

Schneider, Daniel W. "Local Knowledge, Environmental Politics, and the Founding of Ecology in the United States: Stephen Forbes and 'The Lake as a Microcosm' 1887." Isis 91, no. 4 (December 2000): 681–705.