Which leafhopper species is recognized as the western grape leafhopper?

The western grape leafhopper is specifically recognized as Erythoneura elegantula. This species is significant in grapevine agriculture as it can pose a threat to grape production by feeding on the sap of grape plants, which can lead to reduced vine vigor and yield, as well as contribute to the transmission of plant viruses.

In the context of the other options provided, they do not match the required species. While Erythoneura variabilis is another species of leafhopper, it is not the one primarily associated with grapes in the western regions. Pseudococcus comstocki and Planococcus citri are both mealybug species and are not classified as leafhoppers at all, making them irrelevant to the question. The focus on Erythoneura elegantula as the correct answer emphasizes its importance in viticulture as the specific leafhopper affecting western grapevines.