Andrew was born on August 20, 1857, in Jackson County, West Virginia, the son of Andrew Evans and Miriam Florence Hopkins. He received his early education in Jackson, West Virginia. In 1893, he received an honorary PhD degree from West Virginia University. On November 18, 1880, he married Adealia S. Butcher of Wood County, West Virginia. They had four children: Roy Samuel, Edwin Butcher, Louise, and Herbert Evans.
Andrew was a bioclimatist, but starting in 1890 he worked as an entomologist at the West Virginia Agriculture Experimental Station and became its director in 1897. During this period he also taught entomology at West Virginia University from 1896 to 1902. On July 1, 1902, he was appointed to be the forest entomologist in charge of forest insect investigations working for the U.S. Department of Agriculture in the Division of Entomology. He was promoted to senior entomologist in 1904. In 1923, he began working in bioclimatics as a specialized researcher, and became collaborator in charge of bioclimatics in 1931.
During his lifetime, he was a member of many scientific organizations and held leadership positions in many of them. He was a fellow of the American Academy for the Advancement of Science, having become a member in 1893, and an emeritus member in 1938, a fellow of the Entomological Society of America, a member of the Association of Economic Entomologists (vice-president in 1900 and president in 1902), first president of the West Virginia Academy of Sciences, president of the Entomological Society of Washington, president in 1920 of the Biological Society of Washington, vice president of the Washington Academy of the Sciences, life member of the American Meteorological Society, honorary member of the Society of Economic Biologists of England, and member of the Cosmos Club.
His writings focused on forest tree insects and Scolytidae, as well as bioclimatics. His work in bioclimatics included development of the bioclimatic law and science of bioclimatics.
Andrew was elected to the Washington Biologists’ Field Club in 1904 and ended his membership in 1912.
Andrew died in 1946.