RELATION BETWEEN TEMPORAL PERSISTENCE OF HOST PLANTS AND WING LENGTH IN LEAFHOPPERS (HEMIPTERA, AUCHENORRHYNCHA)

1. Wing form frequencies in 255 populations of 101 species of leafhopp ers (Auchenorrhyncha) in temporary and permanent habitats were documen ted. 2. The proportion of brachypterous specimens in the leafhopper as semblages on ruderal host plants in temporary habitats (median 2%, ran ge 0-8%) was significantly lower than that on permanent host plants in undisturbed habitats (median 22%, range 0-94%). 3. Leafhopper species typical of temporary habitats were either monomorphic, macropterous, or wing-dimorphic with macropterous forms prevailing in both sexes. 4. Among the eighty-nine species recorded in permanent habitats, forty-f ive species were wing dimorphic. In forty-one dimorphic species, a bra chypterous form prevailed. This prevalence was found for both sexes in thirty-one species, for only females in nine species and for only mal es in one species. 5. The prevalence of brachypters in males, but not in females, found in Anoscopus flavostriatus, is probably the first su ch documented case in Auchenorrhyncha. 6. The hypothesis is proposed t hat in temporary habitats, density-dependent production of macropters in wing dimorphic species is an adaptation to frequent habitat deterio ration caused by factors independent of the density of the species. 7. The predominance of brachypters in permanent habitats indicates that a density-dependent decrease in fitness usually does not offset the po tential decrease in fitness connected with macroptery and dispersal. B ecause of this inability of leafhopper populations to decrease signifi cantly the quality of their resources, a high population density canno t be used as a predictor of future quality of these resources, which i s information essential for efficient dispersal behaviour.