Sorensen asks how it came about that, within the span of forty years, the American entomological community developed from a few gentlemen naturalists with primary links to Europe to a thriving scientific community exercising world leadership in entomological science. He investigates the relationship between American and European entomology, the background of American entomologists, the implications of entomological theory, and the specific links between 19th-century American society and the rapid institutional growth and advances in theoretical and applied entomology.

By the 1880s the entomologists constituted the largest single group of American zoologists and the largest group of ecologists in the world. While rooted in the British natural history tradition, these individuals developed a distinctive American style of entomological investigation. Inspired by the concept of the balance of nature, they excelled in field investigations of North American insects with special emphasis on insect pests that threatened crop production in a market-oriented agriculture. During this period, entomologists described over ten times as many North American insect species as had been previously named, and they consolidated their findings in definitive collections. Employing evolutionary theory, they contributed to the growing understanding of insect migration, mimicry, seasonal dimorphism, and the symbiotic relationship of plant and animal species. Americans also led in the revision of insect taxonomy according to the new principles. Their employment of entomological findings in the practical control of agricultural pests set new standards worldwide. Initially ridiculed as eccentric bug hunters, American entomologists eventually achieved stature as agricultural advisers and as investigators into the origin and nature of life.

Based primarily on the correspondence of American entomologists, Brethren of the Net draws together information from diverse sources to illuminate an important chapter in the history of American science.

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