The article presents materials on the study of the cicadas Laodelphax striatellus Fall. and Muirodelphax aubei Perr.in the Fergana Valley, their morphological and biological characteristics, systematic position, distribution, harmfulness, food connections and peculiarities of their diagnosis. As I.D. Mityaev points out [1], the useful value of cicadas for humans is very insignificant. There is evidence that some peoples eat large singing cicadas, considering them medicinal, or keep cicadas in cages for the sake of their peculiar singing. It is proved that some species of cicadas, in places of their mass reproduction, play a significant role in the permeability of moisture and aeration of the soil, the underground work of their larvae. Larvae and imago of cicadas are a source of food for many animals and they play a certain role in biocenoses. Some species, due to their low abundance and low harmfulness, are not of great practical importance for humans. Most of the cicadas are pests of various agricultural plants [2, pp. 146-150]. As noted by D.A. Azimov, without deep knowledge of the fauna and development of the taxonomy of insects, as well as other groups of fauna and vegetation, it is impossible to solve further problems of protection and rational use of useful forms, as well as organization of plant protection [3, pp. 54-55]. Therefore, the study of cicadas and their diagnosis is not only theoretical, but also practical.