Harrison Gray Dyar Jr. (February 14, 1866 – January 21, 1929) was an American entomologist. Dyar's Law, a pattern of geometric progression in the growth of insect parts, is named after him. He was also noted for eccentric pursuits which included digging tunnels under his home. He had a complicated personal life and along with his second wife he adopted the Baháʼí Faith. Early life Dyar was born in Linwood Hill, Rhinebeck, New York, to Harrison Gray Dyar and his wife Eleonora Rosella (). His father made a fortune as a chemist and inventor, and upon his death in 1875, left Dyar and the family financially independent. He wrote ghost stories for his sister Perle while his mother took a keen interest in spiritualism. The household also included Lucy Hudson, a homeopath who had a relative, George Henry Hudson (1855-1934) who inculcated Dyar with an interest in natural history. He also learned music and playing the piano from the Hudson family. In 1880 the family moved to Boston and he attended Roxbury Latin School. Dyar went to DeGarmo Institute around 1882, founded by James M. DeGarmo who also maintained a large collection of butterflies. Dyar passed the entrance to Harvard and the Massachusetts Institute of Technology and chose the latter. He graduated from MIT in 1889 with a Bachelor of Science degree in chemistry. He had begun to study insects as a young teenager, and soon after his graduation from college began publishing scientific papers about them, in particular moths of the family Limacodidae, starting a lifelong interest in entomology. He joined a course in embryology at the Woods Hole Biological Station in 1893, and subsequently Columbia University where he trained under Henry Fairfield Osborn, and where he was influenced in eugenics. He was awarded a Master of Arts degree in biology from Columbia University in 1894, with his thesis on the classification of Lepidoptera, and a doctorate in 1895, with his dissertation on airborne bacteria in New York City under the supervision of Theophil Mitchell Prudden. He was also encouraged by his sister Perle's husband S. Adophus Knopf as careers in insect taxonomy were rare. After his PhD he worked on the classification of Lepidoptera based on caterpillar morphology. Taxonomy Dyar's lepidoptera collecting brought him in contact with Ferdinand Heinrich Herman Strecker and the Boston Society of Natural History where he was in contact with Joseph Albert Lintner and