CHORDOTONAL SENSILLJE 



141 



briefly the nature of the sensory organs coneerned. These may 

 be grouped under the general term of chordotonal organs, which 



Fig. 60. A. Section through presumed gustatory organ of an 

 Hemipteron {Graphosoma lineatum). (Adapted from Bugnion 

 and Popoff.) B. Diagram of a simple chordotonal organ con- 

 sisting of a single sensilla. C. Diagrammatic longitudinal 

 section through the second antennal segment of a Geometrid 

 moth (left side), showing Johnston's organ, (Adapted from 

 Eggers.) a, articular membrane ; ab, apical body ; al, axial 

 fibre ; c, cap-cell ; cu, cuticle ; e, envelope-cell ; h, hypo 

 dermis ; /, ligament ; n, antennary nerve and branches 

 n^, n^, to Johnston's organ ; p, cu^icular pore ; s, sense-cell 

 sc, scolopala ; i', vacuole. 



imphes the presence of chords or filaments sensitive to tones or 

 vibrations. 



Chordotonal Sensillae. The sensillae composing chordotonal 

 organs may occur singly, but more often in small groups, or larger 

 numbers may be combined to form more elaborate structures. 



