and a second by Kerteszia, Lophopodomyia, and Nyssorhynchus. Subgenus Stethomyia is an outlier with respect to these two taxa. Within the second group, Kerteszia and Nyssorhynchus appear to be sister taxa. Cellia appears to be more closely related to the Kerteszia-Lophopodomyia-Nyssorhynchus group than to Anopheles or Stethomyia, tentatively suggesting the following branching order: ( Stethomyia ( Anopheles ( Cellia ( Lophopodomyia ( Kerteszia, Nyssorhynchus))))). The number of species currently recognised within the subgenera is given here in parentheses: Anopheles (206 species), Baimaia (one), Cellia (239), Kerteszia (12), Lophopodomyia (six), Nyssorhynchus (34) and Stethomyia (five). The subgenus Baimaia may be elevated to genus level, as it appears to be a sister group to Bironella and all other Anopheles. The ancestors of Drosophila and Anopheles diverged . The Old and New World Anopheles species subsequently diverged between 80 and . Divisions below subgenus Taxonomic units between subgenus and species are not currently recognised as official zoological names. In practice, a number of taxonomic levels have been introduced. The larger subgenera (Anopheles, Cellia, and Nyssorhynchus) have been subdivided into sections and series, which in turn have been divided into groups and subgroups. Below subgroup but above species level is the species complex. Taxonomic levels above species complex can be distinguished on morphological grounds. Species within a species complex are either morphologically identical or extremely similar and can only be reliably separated by microscopic examination of the chromosomes or DNA sequencing. The classification continues to be revised. The first species complex was described in 1926 when the problem of nontransmission of malaria by Anopheles gambiae was solved by Falleroni, who recognised that An. gambiae was a complex of six species, of which only four could transmit malaria. This complex has subsequently been revised to a total of seven species of which five transmit malaria. Subgenus Nyssorhynchus has been divided in three sections: Albimanus (19 species), Argyritarsis (11 species) and Myzorhynchella (four species). The Argyritarsis section has been subdivided into Albitarsis and Argyritarsis groups. The Anopheles group was divided by Edwards into four series: Anopheles (worldwide), Myzorhynchus (Palearctic, Oriental, Australasian and Afrotropical), Cycloleppteron (Neotropical) and Lophoscelomyia (Oriental); and two groups, Arribalzagia (Neotropical) and Christya (Afrotropical). Reid and Knight (1961) modified this classification by subdividing the subgenus Anopheles into two sections, Angusticorn and Laticorn and six series. The division was based on the shape of their pupal trumpets. The Laticorn section was created for those species