Buffalo Treehopper

Stictocephala bisonia — the buffalo treehopper — is one of the strangest small insects in eastern North American backyards and one of about 3,500 species in family Membracidae (the treehoppers — a family famous for extreme pronotum modifications). The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Mexico, and was introduced to Europe in the early 1900s where it is now established across most of temperate Europe. Adults are 6-8 mm long, bright leaf-green coloration, with the species' diagnostic feature: the PRONOTUM (the dorsal segment behind the head) is enlarged into a dramatic TRIANGULAR HORN-LIKE PROJECTION that extends upward and forward over the head and back over the abdomen. The horn shape exactly resembles a miniature bison's horns or a rhinoceros's horn — the source of the common name 'buffalo' (the species name 'bisonia' is also a reference to the bison-like appearance). The pronotum modification is one of the most extreme examples of BODY-PART HYPERTROPHY in any insect and is a flagship case study in family Membracidae's renowned 'pronotum-as-canvas' evolutionary diversity. Family Membracidae includes some of the most extraordinary morphological modifications in the insect world: the BRAZILIAN TREEHOPPER (Bocydium globulare — already in the Wild Files) has a pronotum modified into a multi-balled antenna-like structure, OAK TREEHOPPER (Platycotis vittata) has an arched horn, ANT-MIMIC TREEHOPPERS (various Membracidae) have pronotum modifications shaped like ants, THORN MIMIC TREEHOPPERS have pronotum modifications shaped exactly like plant thorns, and others have pronotum modifications shaped like leaves, fruits, or even other insects. The biological function of the buffalo treehopper's pronotum projection is debated — possibilities include camouflage (the projection breaks up the insect's silhouette against tree bark), mimicry (resembling thorns or other inedible objects), defense (the rigid pronotum may deflect bird beak strikes), or sexual selection (males and females have similar pronotums but the sexes differ slightly in projection size). The species is a minor pest of fruit trees and ornamental shrubs — egg-laying females cut slits in young twigs to insert egg masses, causing twig damage and occasional twig dieback. The species is harmless to humans (no bite, no sting) but is one of the most-photographed treehoppers in NA macro nature photography because of the dramatic morphology.