538 



INSECTA. 



as nervi respiratorii or transversi, is to be regarded as a true sympa- 

 thetic. These nerves are given off near one of the ganglia of the 

 ventral chain from a median nerve which runs between the two 

 ventral nerve cords, has a root in the ganglion, and sometimes forms 

 a small sympathetic ganglion. After their separation they again form 

 lateral ganglia, the nerves of which pass into the lateral nerves, but 

 afterwards separate again from the latter, and after forming plexuses 

 supply the tracheal trunks and muscles of the stigmata. 



Of the Sense organs, the eyes* attain the highest grade of per- 

 fection. The unicorn eal ocelli are principally present in larval life, 

 but two or three of them are often present on the top of the head of 

 fully-developed insects (fig. 87). The facetted eyes are placed at 

 the sides of the head, and are found in the fully- 

 developed insect (fig. 85). 



Auditory vesicles with otoliths have not been dis- 

 covered in insects. Since, however, the capacity of 

 perceiving sound can scarcely be doubted for numerous 

 insects, and especially for those which are capable of 

 producing sound, we are forced to presuppose the 

 existence of some organ for the perception of sound. 

 In fact', in the springing Orf.l>j>tcra apparatuses can 

 be pointed to which probably serve as acoustic organs 

 for the perception of sound waves. In the Acridice 

 these are placed at the .--ides of the first abdominal 

 segment close behind the metathorax (fig. 60, A), in 

 the Gnjllodace and Locustidw in the tibite of the 

 anterior legs, just beneath the articulation of the 



FIG. 4-tK. Tibia 

 of the anterior 



ley 



f emom / 445 \ j n t hi s re gion a tracheal trunk 

 of Loeittttt 



a (after dilates between two lateral membranes so as to form 



v.Graber). Ty, >y ves icle, on which are spread out the end cells, pro- 



tympanic mem- 



brane with oper- vided with so-called nerve rods, of a nerve springing 



from the first thoracic ganglion (fig. 447). Peculiar 

 sense organs have also been discovered in the posterior wings of 

 beetles and in the halteres of fiies. 



Shining nerve rods have been found by Ley dig in the nerves of 



* Compare especially Leydig, ' Znrn feiuereu Ban iler Arthropoden, sowie 

 Gernehs-imd GehoroEgaue tier Krebs<_- mid Inset-ten." Miilh-rK Archir, 1855 and 

 1860. 



H. Grenadier, " Untersnchungen liber das Sehorgan der Arthropoden." 

 Gb'ttingen, 1879. 



Also V. Graber, ''Die tympanalen Siunesorgane der Orthopteren/' Wicn, 

 1875. 



