410 



ARTHROPODA 



beetles) in the position of the later compound eyes. Of other sense organs 

 only the tactile hairs of the skin are known with certainty, while similar 

 hairs on the antenna.' and about the mouth are supposed to be organs of 

 smell and taste, since these senses are known to be well developed. The 

 tvmpanal organs of the Orthoptera are the only structures which can be 



ik 6g. ilCf. I tcjf. 



dig 



FIG. 440. Viscera of male cockroach (Peri planet a orientalist (partly after Huxley). 

 I III, segments of thorax and corresponding legs; i-io, abdominal segments; a, anus 

 ag, ventral ganglia; ap, gastric oeca; at, antenna; bl, salivary bladder; g, sexual opening 

 h, heart; kr, crop; km, gizzard; I, labial palpus; m, stomach (the arrow shows the con 

 nection between m and km), also maxillary palpus; mg, male genitalia; oe, oesophagus 

 og, brain; r, rectum; sp, salivary gland; tg, thoracic ganglia, ug, infracesophagea 

 ganglion; vm, Malpighian tubules. 



with much probability connected with hearing. These are thin drum-like 

 parts of the chitin, framed in thicker portions (figs. 450, 451), beneath 

 which is a tracheal vesicle, with a nerve ending in a 'crista acustica.' End 

 organs similar to those of the criste acusticae occur elsewhere than in the 

 tympana! organs and are regarded as auditory (' chordotonal' sense organs). 



FIG. 450. FIG. 451. 



FIG. 450. Side view of grasshopper, s, spiracles; I, tympanal organ. 

 FIG. 451. Anterior tibia of a Locustid with tympanum, /; (from Hatschek, after 

 Fischer). 



The power of producing sound is widely distributed and often highly 

 developed, the organs for this purpose varying widely in character. 

 Stridulating organs are formed by ridges on wings and legs, which are 

 rubbed against each other or against similar ridges on the body. Hum- 

 ming is produced by the action of the wings or by the passage of air 



