Fig. 4

Leg chordotonal organs (COs) of Monochamus alternatus. a Photograph of female adult in resting posture, and diagram indicating the locations of COs in a femur (c), a tibia (b, f), and a tarsus (g). b Retrograde nerve staining of the prothoracic tibia showing absence of subgenual organ (b in a). c–e The FCO scoloparia (indicated by red arrows) in the prothoracic (c), mesothoracic (d), and metathoracic (e) legs. The cuticular apodeme is indicated by dotted lines. The FCO scoloparium in the metathoracic legs was located more distally compared with those in the pro- and mesothoracic legs. (f) The tibial CO in the distal region of the mesothoracic leg (f in a). g The tarsal CO in tarsal segment III of the metathoracic leg (g in a). h The prothoracic FCO scoloparium viewed posteriorly. i Three-dimensional reconstruction of the scoloparium h, viewed anteriorly. j High-power confocal stacks of the FCO in the mesothoracic leg. Pairs of cell bodies (arrowheads) inserted into common scolopale caps (arrows) are shown with different colors. k Magnified view of the tibial CO (f). l Magnified view of the tarsal CO (g)