John Merton Aldrich was born Jan. 28, 1866, in Olmsted County, Minnesota, and went to school in Rochester (where there is a Unitarian church founded in 1866). He graduated from South Dakota State University in 1888, and received his M.S. there. In 1893, John founded the Department of Zoology at the University of Idaho. He married Ellen Roe of Brookings, South Dakota, and they lived in Moscow, Idaho.
After four years of marriage, his wife and infant son died, and he lost himself in his researches on insects of the order Diptera, or true flies. On June 28, 1905, he married Della Smith of Moscow, Idaho. He then took a year of sabbatical leave, went to Stanford University to study, and received his Ph.D. in May, 1906. While at Sanford, he was active in the formation of the Unitarian Church of Palo Alto.
One of the pre-eminent entomologists of his day, he became Associate Curator and Custodian of Diptera at the Smithsonian Institute, Washington, D.C., and became a member and trustee of All Souls Unitarian Church in Washington. He died May 7, 1934, just before setting out on a collecting trip to the West Coast.