ON ABDOMINAL SEGMENTS. 231 



but he gives no figure. In Fig. 8 I have represented 

 the junction of the second and third abdominal seg- 

 ments in Lasius flavus, x 225, as shown in a longi- 

 tudinal and vertical section. There are about ten 

 well-marked ribs (r), occupying a length of approxi- 

 mately yq-o of ^^ inch. Similar ridges also occur 

 between the following segments. 



In connection with the sense of hearing I may 

 mention another very interesting structure. In the 

 year 1844, Von Siebold described ' a remarkable organ 

 which he had discovered in the tibiae of the front legs 

 of Gryllus, and which he considered to serve for the 

 purpose of hearing. These organs have been also 

 studied by Burmeister, Brunner, Hensen, Leydig, and 

 others, and have recently been the subject of a mono- 

 graph by Dr. V. Graber,^ who commences his memoir 

 by observing that they are organs of an entirely unique 

 character, and that nothing corresponding to them 



Fig. 9. 



Tibia of Lasius flavus ^ x 75. 



occurs in any other insects, or indeed in any other 

 Arthropods. 



' Ueber das Stimm. mid GeMrorgan der Ortliopteren, Wicg- 

 mami's Art.f. JVafnr., 1844. 



" Die Tgmj)anaJe)i Sinnesapparate der Orthopieren! von Dr 

 Vitus Graber, 1875. 



