Frederick Vincent Theobald FES was an English entomologist and "distinguished authority on mosquitoes". During his career, he was responsible for the economic zoology section of the Natural History Museum, London, vice-principal of the South-Eastern Agricultural College at Wye, Kent, Professor of Agricultural Zoology at London University, and advisory entomologist to the Board of Agriculture for the South-Eastern district of England. He wrote a five volume monograph and sixty scientific papers on mosquitoes. He was recognised for his work in entomology, tropical medicine, and sanitation; awards for his work include the Imperial Ottoman Order of Osmanieh, the Mary Kingsley Medal, and the Victoria Medal of Honour, as well as honorary fellowships of learned societies.

Mosquitoes, the Culicidae, are a family of small flies consisting of 3,600 species. The word mosquito is Spanish and Portuguese for little fly. Mosquitoes have a slender segmented body, one pair of wings, three pairs of long hair-like legs, and specialized, highly elongated, piercing-sucking mouthparts. All mosquitoes drink nectar from flowers; females of some species have in addition adapted to drink blood. Evolutionary biologists view mosquitoes as micropredators, small animals that parasitise larger ones by drinking their blood without immediately killing them. Medical parasitologists view mosquitoes instead as vectors of disease, carrying protozoan parasites or bacterial or viral pathogens from one host to another.