 Chordotonal organs can be composed of a single scolopidium with only a single sensory, bipolar neuron (such as the tympanal ear of a notodontid moth), or up to several thousand scolopidia, each equipped with up to four sensory neurons (as in the mosquito Johnston's organ).The bipolar sensory neurons each have an apical dendritic structure with a cilium densely packed with microtubules and surrounded by two specialized cells, the scolopale cell and the attachment (cap) cell, plus a glial cell.Mechanically gated ion channels are located distal to the ciliary dilation, a characteristic part of the upper dendiritic cilium.