Alexandr Rasnitsyn was born on 24 September 1936 in Moscow. As a schoolboy Alex was active in the Society of Young Biologists at the Moscow Zoo. In 1955 he became a student at the Biological Faculty of the Moscow State University and in 1960 he graduated with honors from the Department of Entomology. His Master thesis was "Hibernation in the ichneumon-fly subfamily Ichneumoninae". The same year Rasnitsyn joined the Laboratory of Arthropods at the Paleontological institute, Academy of Sciences of USSR. In 1967 he received his Ph.D. in biology from the Paleontological Institute with the thesis "The Mesozoic Hymenoptera Symphyta and the early evolution of Xyelidae". After defending in 1978 his Dr. hab. (doktor nauk) thesis "The origin and evolution of Hymenoptera" Rasnitsyn became Head of the Laboratory of Arthropods. In 1991 he received the title of a Biology Professor. In 1996 he resigned from heading the Laboratory and continued there as a principal research worker, but after the new leader, Vladimir Zherikhin, died in 2001 Rasnitsyn again became the acting Head of the Laboratory (2002—present).
