He went to the University of Alberta to study carabid beetles under George Ball, obtaining a Ph.D. in 1969 followed by a post-doctoral stint at Harvard under P. Jackson Darlington, Jr.
He took up an entomologist position in the United States National Museum (later the Smithsonian Institution) but took a year off to study carabid beetles at the University of Lund under Carl H. Lindroth.
By fogging the forest canopy with pesticide, he collected the falling specimens and found 1,200 species of beetles living in Luehea seemannii trees.
Erwin estimated that there are about twice as many species of insects and related animals in tropical trees as there are on the ground of the forest.
[4][5] Erwin served as secretary of the Society of Systematic Biologists from 1973 to 1975,[6] and was the editor in chief of ZooKeys.