To the color variation in the common green grasshopper (Omocestus viridulus, Orthoptera: Acrididae)

In spite of being an important factor in determining the nature of interactions between the animal population and its habitat, the phenomenon of polymorphism is still insufficiently considered when studying the life forms of animals including grasshoppers. In particular, variation in the different phenotype ratios of a population can be an effective mechanism of its rapid adaptation to the changing habitat conditions. Therefore, the investigation of the cryptic colour polymorphism of grasshoppers Omocestus viridulus in the different parts of the species area is of particular interest. We studied the colour variability of the common green grasshopper Omocestus viridulus. The research was conducted in the Pskov and Novgorod regions of Russia in 2015 and 2017. The ratio between different colour types of species was determined by counting grasshoppers on transects in ten geographical locations. A total of 1,166 individuals were registered. Three typical colour forms of O. viridulus are typical in the north-west Russia: f. rubiginosa (without green components in colouring), f. hyalosuperficies (green colour is only on the top of the body) and f. viridis (green colour is predominant). It was stated that most of the males were classified as f. rubiginosa whereas most of females as f. hyalosuperficies in all investigated locations. Individuals of both males and females of f. viridis were rarely found in all 9 locations in the Pskov Region. In the Novgorod region in the only studied location they were not found at all. The proportion of f. viridis individuals was approximately the same for all the locations in the Pskov region. It ranged from 4.8 to 11.2% of the total number of counted individuals and did not depend on animals’ sex. Within the Pskov Region no statistical differences were found in the proportion of f. viridisin in various locations. Nevertheless, it differed significantly from the result that was obtained in the Novgorod region, as well as from the Scandinavian data available in the literature. The reason for these differences is not quite clear, and a further investigation is needed to find a convincing explanation.