Treehoppers (more precisely typical treehoppers to distinguish them from the Aetalionidae) and thorn bugs are members of the family Membracidae, a group of insects related to the cicadas and the leafhoppers. About 3,200 species of treehoppers in over 400 genera are known. They are found on all continents except Antarctica; only five species are known from Europe. Individual treehoppers usually live for only a few months. Morphology Treehoppers, due to their unusual appearance, have long interested naturalists. They are best known for their large pronotum, expanded into often strange shapes that enhance their camouflage or mimicry, often resembling plant thorns (thus the commonly used name of "thorn bugs" for a number of treehopper species). The specialised pronotum (or helmet) may not be simply an expansion of the prothoracic sclerite, but a fused pair of dorsal appendages of the first thoracic segment. The treehopper has specialized muscles in its hind femora that unfurl to generate sufficient force to jump. These may be serial homologues of insect wings, which are dorsal appendages of the second and/or third thoracic segments, although this interpretation has been seriously challenged. Evidence for this theory included the development of the helmet, which arises as a pair of appendages attached to each side of the dorsal prothorax by an articulation with muscles and a flexible membrane that allow it to be mobile (also, similar genes are involved in development of the helmet and the wings). Distinguishing males from females is accomplished only by looking at the genitalia. Ecology Treehoppers pierce plant stems with their beaks and feed upon sap. The young can frequently be found on herbaceous shrubs and grasses, while the adults more often frequent hardwood tree species. Excess sap becomes concentrated as honeydew, which often attracts ants. Some species have a well-developed ant mutualism, and these species are normally gregarious as well, which attracts more ants. The ants provide protection from predators. Treehoppers mimic thorns to prevent predators from spotting them. Others have formed mutualisms with wasps, such as Parachartergus apicalis. Even geckos form mutualistic relations with treehoppers, with whom they communicate by small vibrations of the abdomen. Eggs are laid by the female with her saw-like ovipositor in slits cut into the cambium or live tissue of stems, though some species lay eggs on top of leaves or stems. The eggs may be parasitised by wasps, such as the tiny fairyflies (Mymaridae) and Trichogrammatidae. The