Charles William Lacaillade (1904-1978) was an eminent biologist in the middle decades of the twentieth century. He was born in Lawrence, Massachusetts of parents whose ancestors were French Canadians. His father, also named Charles William Lacaillade, was a dentist who graduated from Tufts University School of Dentistry in 1898. His mother, Elodia Eno, came from a family of very successful businessmen. Lacaillade was the third of six children. His two older brothers, Harold Carleton and Hector Eno, both graduated from the University of Louisville, School of Dentistry, while his younger brother, Lawrence, became a businessman. His sister, Luemma, married Dr. Henry Steadman, a veterinarian, while his youngest sister, Gloria, married a U.S. Army officer, Lieutenant Colonel Victor Anido. Lacaillade received his MS and PhD degrees in biology and zoology from Harvard University. He then became a fellow at The Rockefeller Institute for Medical Research. At both institutions, he studied under some of the most eminent biological scientists of the time. These included Rudolf W. Glaser, George Howard Parker, Theobald Smith, Carl TenBroeck, and William Morton Wheeler. At the Rockefeller Institute, he co-discovered the vector and mode of transmission of Eastern Equine Encephalomyelitis. This discovery, and the research he conducted with Rudolf W. Glaser, quickly established him as an outstanding biological researcher. However, a change in leadership at the Rockefeller Institute resulted in research priorities being given to the disciplines of general physiology, physical chemistry, and nutrition. This shift in the research agenda away from the biological sciences precluded career advancement at the Rockefeller Institute for post-doctoral fellows like Lacaillade. It was the height of the Great Depression, and even biologists with terminal doctoral degrees found it difficult to find positions. In 1935, Lacaillade accepted a position as an assistant in biology at St. John's College in Brooklyn, New York. Although a small single-gender college for men, the Department of Biology there under Dr. Andrew I. Dawson had an impressive record of research achievements. Lacaillade remained at this institution for the remainder of his career until his retirement in 1970. He eventually became Distinguished Professor of Biology, Chair of the Department of Biology, and the recipient of numerous awards and recognitions. Lacaillade quickly developed a reputation as an outstanding teacher, mentor, and scientist. He taught introductory courses in biology as well as advanced ones in parasitology and entomology. He preceptored graduate students and guided their dissertation research. Above all else, he was a superb mentor who provided sage advice to pre-professional students planning careers in medicine and dentistry. Lacaillade effortlessly adapted to the transformation of St. John's College, with an annual enrollment of some 600, to St. John's University, with an average annual student census of 20,000. He also oversaw the geographic relocation of his department from Brooklyn to the then new campus in Jamaica, New York in 1955. He proved to be a stabilizing presence during the faculty strike of 1966 and its aftermath which included a reorganization of the university. Throughout his life, Lacaillade was admired as a man of letters. His interests spanned art, literature, opera, and the theater. He had a passionate interest in English literature, about which he wrote, and was proud of his collection of first editions of English writers. Charles William Lacaillade was an eminent success as a research biologist early in his career. However, his greater successes came later as an outstanding educator and mentor. As such, he had a positive and lasting influence on the lives and careers of many students and colleagues. He passed away on 17 September 1978 in Danvers, Massachusetts.