Morphs of Philaenus species, candidate Xylella fastidiosa vectors

The genus Philaenus presents a well-known colour polymorphism, allowing discrimination of morphs and engaging non-skilled practitioners in species identification. This study considers a collection of approximately 2500 Philaenus spp. individuals from southern Italy and northern Tunisia. We felt a morph valid if in our collection or recorded in a minimum of two different references from different geographical locations or timepoints. Reviewing the literature for phenotypes allowed the development of a key to discriminate between the 25 available phenotypes. The study suggests that Philaenus spumarius has twenty-three morphs, followed by the eight morphs of Philaenus signatus, the seven of Philaenus tesselatus, the six of Philaenus italosignus, Philaenus maghresignus, and Philaenus tarifa, the two of Philaenus loukasi, and one of Philaenus arslani. P. maghresignus and P. tesselatus show all morphs cited in the literature plus a gibba morph based on single female individuals. P. spumarius was absent from Tunisian collections; therefore, all data on P. spumarius rely on Italian specimens. De-greasing revealed the true phenology of individuals, allowing the classification of ambiguous individuals. Light microscope and SEM observations in P. spumarius recently collected in southern Italy (Apulia region) revealed six concave hairless spots on the pronotum corresponding to the dark spots of impressa morph, a morph hitherto only known from North America only. Xylella fastidiosa was isolated and described in Nearctic. The recent finding of impressa morph in Italy may suggest a different route of bacterium introduction in the Old Word by adult vector importation.