We documented one of the most species-rich assemblages of tropical rain-forest Auchenorrhyncha, comprising 402 phloem- and xylem-feeding species, by sampling adults from forest vegetation. Further, we reared 106 species from larvae sampled on 14 plant species. Both xylem- and phloem-feeding guilds exhibited wide host-plant ranges, as 74% of species fed on more than one plant family. In comparison, using data extracted from the temperate-zone literature, phloem-feeders exhibited lower host specificity in Papua New Guinea than in Germany, because in Papua New Guinea they were dominated by generalist Fulgoroidea while in Germany by specialist Membracoidea. The similarity of Auchenorrhyncha assemblages from different plant species was unrelated to the phylogenetic distance between their hosts. Host specificity, abundance and species composition of Auchenorrhyncha assemblages were unrelated to the optimum of their host plant species on succession gradient from secondary to primary forest. Higher host specificity did not lead to greater species richness in Auchenorrhyncha assemblages feeding on different plant species, but the number of species feeding on a particular plant species was a strong predictor of the Auchenorrhyncha abundance on that plant. These patterns suggest that Auchenorrhyncha assemblages on these plant species are not saturated with species and determined by division of limited resources among competitors, but instead are dependent on the number of colonizers from the regional species pool.

A survey of planthopper and leafhopper assemblages and insect predators was conducted in the rice fields of Kaluvanchikudi in Batticaloa District and Kohabana and Central Camp in Amparai District during the dry (yala) season in 1989. Nilaparvata lugens (Stål) was the predominant planthopper species in these rice fields; Sogatella furcifera (Horvath) comprised less than 10% of the sample in any field. The leafhopper species collected included Nephotettix nigropictus (Stål), Nephotettix virescens (Distant), Recilia dorsalis (Motschulsky), and Cofana (= Tettigella) spectra (Distant). Nephotettix species were predominant in Kaluvanchikudi and Kohabana, while R. dorsalis was dominant in Central Camp. Insect predators included the mirid, Cyrtorhinus lividipennis Reuter, an anthocorid, Onus tantillus (Motschulsky) and two coccinellids, Harmonia octomaculata (Fabricius) and Micrapsis discolor (Fabricius). Application of furadan granules reduced the planthopper and leafhopper populations drastically, but did not appreciably reduce the insect predator population.