J. M. (John Merton) Aldrich was born on January 28, 1866, in Olmstead County, Minnesota, to Levi O. and Mary Moore Aldrich. He was educated in the county and high schools of Rochester, Minnesota. In 1885, he enrolled at Dakota Agricultural College in Brookings, South Dakota, and became the first student to specialize in zoological sciences. He graduated in 1888, receiving his B.S. degree during the institution’s first formal commencement ceremony.

Following his graduation, Aldrich remained at Dakota Agricultural College as an Assistant in Entomology (1889–1890), then as an Assistant in Zoology (1890–1892), and also assisted the Agricultural Experiment Station Entomologist during this period. He pursued further academic credentials, earning additional B.S. and M.S. degrees from the University of Kansas, and later, in 1906, a Ph.D. from Stanford University. His doctoral dissertation was his influential Catalog of North American Diptera, which he began while serving as Professor of Zoology at the University of Idaho (1893–1913).

After leaving the University of Idaho in 1913, Aldrich joined the U.S. Department of Agriculture Bureau of Entomology in West Lafayette, Indiana as an Entomological Assistant. In 1918, he was transferred to the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., where he served as Custodian of Diptera and Associate Curator in the Division of Insects. He was the first Dipterist hired at the Smithsonian who had previously served in the USDA.

Aldrich was internationally recognized for his ability to collect rare insect specimens across the western United States, Alaska, and Guatemala. Many of his finds were previously unknown to science. His expertise in North American Diptera positioned the National Museum as a leading research center for New World Diptera. In 1923, he donated his personal collection of over 45,000 insect specimens, representing more than 4,000 taxa, along with a detailed card catalog of North American Diptera literature. This resource became one of the most valuable general Diptera collections in the museum.

He published extensively on entomological subjects and served as President of the Entomological Society of America in 1921. He received numerous accolades during his lifetime. Aldrich passed away in 1934. His legacy endures, notably through the Aldrich Entomology Club, founded in 1961 at the University of Idaho, which continues to promote engagement in insect biology among students, faculty, and the public.