When compared with the aphids (Aphidoidea) and scale insect groups (Coccoidea), whiteflies (Aleyrodoidea) living today appear to be a much less species-rich assemblage. The present collation has resulted in some 1556 available species names, in comparison with over 4500 aphidoids (Remaudière & Remaudière, 1997; Blackman & Eastop, 2006) and over 7000 coccoids (Miller & Ben Dov, 2003). This apparent paucity of species is unlikely to reflect reality, however. Whiteflies have suffered from a particularly problematical systematic history (Martin, 2003), which has undoubtedly diverted the attentions of many systematists elsewhere. In particular over a century of taxonomy based almost solely on the final nymphal (“puparial”) stage, with many characters untested for their importance and significance, has not encouraged more systematists to become involved with the group.

(Extract from: Martin & Mound, 2007)