Dispersal by flight of leafhoppers (Auchenorrhyncha: Homoptera).
One-third of the total of British species of Auchenorrhyncha have been identified in aerial traps at Silwood Park, in southern England. The numbers of leafhoppers in annual catches in traps are small compared with those of other insects, and about half of them are composed of Macrosteles sexnotatus (Fall.), M. laevis (Ribaut) and Javesella pellucida (F.), which are known vectors of plant diseases. Patterns of dispersal have been examined in several species and related to voltinism and to the seasonal incidence of adults. Of the Cicadellidae taken in aerial traps, 10% were tree-dwellers; this may be related to the permanency of their habitats. Also, tree-dwellers occurred in greater numbers in higher than in lower traps, whereas the reverse was true of the grassland species. This indicates differences in dispersal patterns of leafhoppers from different habitats. Many species show alary polymorphism. Some exhibit extreme brachyptery and macroptery, the long-winged, migratory females showing delayed maturation; in another group, ability to fly was linked with the ratio of the lengths of fore- and hind-wings. Flyers and non-flyers were distinguished by laboratory tests. In a third group, all individuals were macropterous, but some had extra-long wings and were the only morphs caught in aerial traps. Individuals of most or all species dispersed when they were immature. In many species, males and females dispersed in equal numbers. In those where macroptery was rare, the long-winged individuals were all females. In a few species, greater numbers of males than females were caught in aerial traps. Parasitised leafhoppers dispersed by flight, at least while the internal parasitic larvae were still small. Thus, in invading and colonising new breeding sites, some regulatory mechanisms of leafhopper populations were transmitted together with the host species.