1. The chromosomes of the cicadellid species Xerophloea viridis (2n=18+XY) and of species belonging to related genera, are far larger than the chromosomes of any other species belonging to the Auchenorrhyncha so far cytologically studied. 2. In X. viridis, at diplotene (and in Ulopa reticulata, a related species, at pachytene), the chromosomes of the bivalents show a banded appearance somewhat like that seen in the primary polytene chromosomes in the young larvae of many Dipteran species. It is suggested that a relatively high degree of polyteny is responsible for the peculiar spiralization patterns in the meiotic prophase of X. viridis. 3. In X. viridis (and in Eupelix cuspidata, a related species) the chiasmata arise at a stage when the bouquet orientation still persists. 4. The chiasma frequency is low in the Auchenorrhyncha. In many cases, a lowering of the recombination index has taken place during the chromosomal evolution of a genus or tribe. It is suggested that chiasmata are of universal occurrence in the Auchenorrhyncha. 5. The amount of DNA contained in the nuclei of Graphocephala coccinea (2n=22+X), another member of the family Cicadellidae, is about one-fourth of that contained in the nuclei of Xerophloea viridis (2n=18+XY) at the same stages. 6. Probably Xerophloea and other primitive genera with large chromosomes have retained the ancestral amount of DNA. typical of the family Cicadellidae at the time when more advanced tribes began to develop. This implies that in the line leading to Graphocephala two downward shifts in the DNA content, and in the level of polyteny, have occurred.