Sensory Receptors Associated with the Labial Tip and Precibarium of Philaenus spumarius L. (Hemiptera: Aphrophoride)

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