Ultrastructure of sensory receptors on the labium of the cassava mealybug, Phenacoccus manihoti Matile Ferrero

The ultrastructure of the sensory receptors located on the labium of the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Homoptera, Pseudococcidae) was studied with scanning and transmission electron microscopes. Trichoid hairs of probable mechanoreceptive function are distributed over the labium. Uniporous chemosensilla which possess a mechanoreceptive dendrite, multiporous chemosensilla and mechanoreceptive pegs are present on the tip of the labium. The presence of contact and olfactory chemoreceptors on the labial tip of P. manihoti suggests that tapping it on the cassava leaf provides the pest with information about the chemical nature of the leaf surface.