Femoral chordotonal organ in the legs of an insect, Chrysoperla carnea (Neuroptera)

The femoral chordotonal organ (FCO) in Chrysoperla carnea is situated in th e distal part of the femur and consists of two scoloparia, which are fused at their distal end. The distal scoloparium contains 17-20 scolopidia, and the proximal one six scolopidia, Each scolopidium consists of two sensory c ells and three types of enveloping cells (glial, scolopale and attachment c ell). The sensory cells of different scolopidia do not lie at the same leve l in the FCO, Therefore the attachment cells of different scolopidia have d ifferent lengths. In the FCO, three types of ciliary roots are found in dif ferent sensory cells. The dendrite of the sensory cell terminates in a dist al process, which has the structure of a modified cilium (9x2+0), The very distal part of the cilium is surrounded by an extracellular electron dense material, the cap, and ends in a terminal dilation. The scolopale cell cont ains the electron dense scolopale rods, consisting of plentiful microtubule s, In their middle third the scolopale rods are fused and form the scolopal e, In the FCO septate junctions, desmosomes and hemidesmosomes are found.