The Cicadomorpha Philaenus spumarius, Neophilaenus campestris, and Cicadella viridis are known transmitters of the bacterium Xylella fastidiosa. Here, we studied the ultrastructural organization of their cephalic glands. Our investigations with scanning, transmission, focused ion beam-scanning electron microscopes and light microscope revealed for the first time in Auchenorrhyncha the presence of two types of cephalic glands. Both belonged to the Class III epidermal glands, according to the Noirot and Quennedey classification. Type A glands were the most common, being mainly located around antennae, lorum, and gena. Moreover, these glands were observed also on the abdomen and thorax, always in association with sensilla trichoidea. The second type of glands (type B) were located exclusively at the apical part of the postclypeus in P. spumarius and N. campestris. The ultrastructural organization was similar in both types, being composed of a secretory cell and a conducting canal. Differences were observed in the width of the cuticular opening, being smaller in the type II glands. In addition, we have recorded the presence of a maxillary sensory pit in all species and described sensilla trichoidea ultrastructural organization. Finally, we discussed the ultrastructural organization of the glands and their potential biological role.

The meadow spittlebug, Philaenus spumarius (Linnaeus) (Hemiptera: Aphrophoridae), is an important vector for the xylem-limited bacterium Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner), which is associated with olive quick decline syndrome in southern Italy. The mouthparts of Hemiptera have important roles in host plant selection, feeding behavior and for vectoring pathogens that cause plant diseases. In this study, the functional morphology of the sensory structures located on the labium tip and precibarium of P. spumarius was investigated using scanning and transmission electron microscopy. The labium tip is composed of two symmetrical sensory complexes, each with five different types of sensilla: aporous sensilla trichodea type 1 and 2; uniporous sensilla chaetica type 1 and 2; and multiporous sensilla basiconica. The precibarium of P. spumarius has two kinds of sensory structures: bulbous sensilla and papillae sensilla. In particular, two groups of sensilla are located on the epipharynx: a distal group that consists of ten papillae sensilla and a proximal group composed of six papillae sensilla and two bulbous sensilla, while the hypopharynx has only two papillae sensilla. The involvement of these sensory structures in the context of feeding behavior and pathogen transmission is discussed.