Histological similarity between proboscis and other appendages. (A-D) Distribution of neurons in four different types of mosquito appendages. Panels represent the merged images of immunostaining of antenna (A), maxillary palps (B), proboscis (C), and leg (D) (blue: nuclei, magenta: HRP-positive neuron). Note the similar large bundles of nerve fibers visualized in each appendage. (E-J) A variety of neurons in mosquitoes' proboscis. Panels represent the localization of HRP-positive neurons (magenta) in the shaft (E) and labellum (F) of the proboscis. The proboscis also contains serotonin-positive neurons (blue: nuclei, green: serotonin) (H-J). Note that there are many sensilla (extra sensory organs) distributed throughout the proboscis (G). All bars: 25 μm.