Identification, sexual dimorphism, and allometric effects of three psyllid species of the genus Psyllopsis by geometric morphometric analysis (Hemiptera, Liviidae)

Abstract. Jumping plant lice (Hemiptera: Psylloidea) are considered important vectors of plant diseases and also economically important pests in agriculture and forest ecosystems. Three psyllid species Psyllopsis repens Loginova, 1963, Psyllopsis securicola Loginova, 1963, and Psyllopsis machinosus Loginova, 1963 associated with the ash tree Fraxinus are morphologically very similar. So far, their distinction has been possible only by comparing their male and female genitalia. In this research, forewing shape and size characteristics, sexual dimorphism and their allometric effects, using geometric morphometric analysis, were examined for identification purposes. The results showed significant differences in wing shape and size between the species studied. Based on the results, two species P. machinosus and P. securicola can be differentiated with the vein M1+2, as in P. securicola the vein M1+2 is located between Rs and M3+4 veins, but the vein M1+2 is closer to the vein M3+4 in P. machinosus; also, P. repens can be differentiated from the two species P. machinosus and P. securicola by vein M. Hence, the veins M1+2, M3+4, Rs and M were the most important wing characters for discrimination of the three species, especially in the field. The analysis also showed significant differences in wing shape and size between male and female of the three species, and the allometric analysis showed that significant shape differences still remain in constant size in P. machinosus and P. repens. Geometric changes in the forewings of both sexes for the three species are illustrated.