Within the subfamily Phlebotominae of the family Psychodidae it is estimated that there are approaching 1000 species and subspecies of sand flies, in five or six genera (depending on whether Psychodopygus is considered a subgenus or genus). Three genera – Phlebotomus, Lutzomyia and Sergentomyia – suck blood from vertebrates, the former two being the more important because they contain disease vectors.

The genus Phlebotomus occurs only in the Old World, from southern parts of northern temperate areas, mainly the Mediterranean region, to central Asia, and in tropical areas, but there are not many species in sub-Saharan Africa or Southeast Asia and none in the Pacific area. Most Phlebotomus species inhabit semiarid and savanna areas in preference to forests. Lutzomyia species are found only in the New World, and, by contrast, occur mainly in forested areas of Central and South America.

Sergentomyia species are also confined to the Old World, being found mainly in the Indian subregion, sub-Saharan Africa and Asia. Although a few species bite people they are not vectors.

The medically most important species include Phlebotomus papatasi, P. sergenti, P. argentipes, P. ariasi, P. perniciosus and species in the Lutzomyia longipalpis and L. flaviscutellata species complexes. In both the Old and New Worlds sand flies are vectors of leishmaniasis and viruses responsible for sand fly fever, and in theAndes the bacterium Bartonella bacilliformis, causing bartonellosis (Carrión’s disease).