INSECT VARIETY. M7 



to a little membranous sac of a cylindrical shape {m), distended 

 with a fluid to which it is united superiorly. This membranous 

 saxj will be directly recognised by the experienced eye as the 

 " membranous labyrinth " of Siebold, and " the thin-skinned 

 bladder filled with water " of Mtiller (Plate II., Fig. 1b) ; but 

 what is most singular is the position it occupies, as it is not, I 

 think, as in grasshoppers and locusts, attached closely to the 

 horny piece or pieces on the disc of the tympanum, but only 

 connected therewith ; while, at the other extremity, it lies on 

 the elevator muscle of the hind wing. From the superior 

 extremity of this membranous labyrinth, proceeds another short 

 process to the upper horny margin of the chamber, where it 

 appears to ramify ; and from the lower issues the auditory nerve 

 («), which proceeds in the direction of the fourth (?) ganglion 

 or nerve-knot, obliquely across and round the elevator muscle 

 (Plate VII., Fig. 3, »). 



By dissevering the abdomen at the junction of the third 

 and fourth segments, and then laying bare the posterior saddle- 

 shaped incasing of the corresponding transverse organs of 

 hearing, a judicious use of the needle-point may be employed to 

 reveal some accessories to the parts ah'eady described (Plate IV., 

 Fig. 9). It will then eventually become clear that above the 

 chamber containing the membranous labyrinth and auditory 

 nerve, parted by a membrane sometimes white with a shining 

 spot, sometimes wholly glassy and iridescent (m), is a second 

 air- vesicle (c), contained in a more or less ovate process, which 

 on either side forms as it were the pommels of the saddle (^) . 

 This second cell will be found, I think, on the one hand, to be 

 in connection with the chamber containing the membranous 

 labyrinth and auditory nerve by means of a little orifice ; while, 

 on the other, it communicates with the external air by a lateral 

 chitineous tube that opens at the side of the abdomen at the 

 junction of the seventh and eighth dorsal arcs, immediately 

 above the conch of the external ear (e) — a premise which 

 leads us to suppose we have here the counterpart of the eustachian 

 tube, designed to balance the atmospheric pressure on the deli- 

 cate membrane of the tympanum. (See Fig. 6.) 



Lastly, there is above or in front of the two central ovate 

 cells, and communicating with them, a third air-cell {d), which 



