After graduation, Marlatt became an assistant professor for two years at Kansas and his skills in drawing insects was noted by
Charles Valentine Riley. Riley recruited him into the
Bureau of Entomology,
United States Department of Agriculture in 1889. He was involved in introduced the
ladybug insect
Chilocorus similis into the
United States to control the
San Jose scale insect, which was first discovered in
San Jose, California in 1880 by
John Henry Comstock and named by him. In 1912, he was appointed chairman of the
Federal Horticultural Board. He was president of the
Entomological Society of Washington in 1897–98 and of the
American Association of Economic Entomologists in 1899. Marlatt's 1907 description of
periodic cicadas remains a classic in the field. In this article, Marlatt proposed a grouping of periodic cicadas into 30 different broods, each given a
Roman numeral. Broods I–XVII assigned brood numbers for each of 17 sequential calendar years to 17-year cicadas. Broods XVIII–XXX assigned 13 sequential calendar years to 13-year cicadas. Subsequent research has established that, in fact, not every year produces a brood of periodical cicadas. There are only 15 distinct broods, not 30, but Marlatt's scheme continues to be used. In Marlatt's role as chief of Chief of the Plant Quarantine and Control Administration he became involved in the passing of the Plant Quarantine Act which was finally passed in 1912. Marlatt and his newly-wed wife travelled to China and Japan in 1901–2 in search of the natural enemies of the San Jose scale. His wife became ill due to an unknown disease that she contracted on the trip that ultimately caused her death. Marlatt became Chief of the Bureau in 1927 following the retirement of
Leland Ossian Howard. In 1922, Marlatt received an honorary doctorate from Kansas State University. He retired in 1938, and died on March 3, 1954, aged 90. == Legacy ==