Ultrastructural Analysis of Johnston’s Organ and Brain Organization in Philaenus spumarius (Hemiptera: Aphrophoridae)

Insects rely on a variety of sensory cues for orientation, with antennae playing a central role in receiving and transmitting information about the environment. <i>Philaenus spumarius</i> (Hemiptera: Aphrophoridae), a spittlebug and vector of the bacterium <i>Xylella fastidiosa</i>, has a reduced number of antennal sensilla, yet demonstrates effective multimodal communication through olfactory and vibrational signals. This study aimed to investigate how the simplified sensory system of <i>P. spumarius</i> relates to the primary neuropils of the brain. We examined the ultrastructural organization of Johnston's organ using scanning and transmission electron microscopy, complemented by previous data on antennal sensilla. Brain organization was investigated by Micro-CT and confocal laser scanning microscopy, which enabled us to identify the primary neuropiles. In addition, we conducted antennal and single sensillum backfills to trace sensory neurons to the brain. Our findings provide insight into the adaptation of a simplified sensory system for effective communication and orientation in <i>P. spumarius</i>.