females of some membracid species sit over their eggs to protect them from predators and parasites, and may buzz their wings at intruders. The females of some gregarious species work together to protect each other's eggs. In at least one species, Publilia modesta, mothers serve to attract ants when nymphs are too small to produce much honeydew. Some other species make feeding slits for the nymphs. Like the adults, the nymphs also feed upon sap, and unlike adults, have an extensible anal tube that appears designed to deposit honeydew away from their bodies. The tube appears to be longer in solitary species rarely attended by ants. It is important for sap-feeding bugs to dispose of honeydew, as otherwise it can become infected with sooty moulds. Indeed, one of the evident benefits of ants for Publilia concava nymphs is that the ants remove the honeydew and reduce such fungal growth. Most species are innocuous to humans, although a few are considered minor pests, such as Umbonia crassicornis (a thorn bug), the three-cornered alfalfa hopper (Spissistilus festinus), and the buffalo treehopper (Stictocephala bisonia), which has been introduced to Europe. The cowbug Oxyrachis tarandus has been recorded as a pest of Withania somnifera in India. Systematics The diversity of treehoppers has been little researched, and their systematic arrangement is tentative. It seems three main lineages can be distinguished; the Endoiastinae are the most ancient treehoppers, still somewhat resembling cicadas. Centrotinae form the second group; they are somewhat more advanced but the pronotum still does not cover the scutellum in almost all of these. The Darninae, Heteronotinae, Membracinae and Smiliinae contain the most apomorphic treehoppers. Several proposed subfamilies seem to be paraphyletic. Centronodinae and Nicomiinae might need to be merged into the Centrotinae to result in a monophyletic group. References Further reading Godoy, C., et al. Membrácidos de la América Tropical (Treehoppers of Tropical America(bilingual, English and Spanish).)''. Santo Domingo de Heredia: INBIO, Inst. Nacional de Biodiversidad. 2006. External links Dietrich, C. H. Treehopper FAQ. Section for Biodiversity, Illinois Natural History Survey, Champaign, IL, USA. 2006. Imagess. Family Membracidae - Treehoppers (United States and Canada). BugGuide. DrMetcalf: a resource on cicadas, leafhoppers, planthoppers, spittlebugs, and treehoppers Deitz, L. L. and M. S. Wallace. 2010. Treehoppers: Aetalionidae, Melizoderidae, and Membracidae (Hemiptera). North Carolina State University Insect Museum. Membracoidea Insect vectors of plant pathogens