PHYSIOLOGY OF THE INVERTEBRATA, 357 



Ortlioptcra, Diptera, Lcpidojjtera, Xctiroptera, Hymcnoptcra, and 

 ( 'olcoptcra., a strong nerve arising from the cerebral ganglion 

 posses into the antennae, and there is a sensory terminal 

 organ, formed by cells developed from the hypodermis, with 

 which the nerve-fibres are connected. The function of this 

 organ was ascertained by extirpating the antenna?, and the 

 insects which turned away from carbolic acid, turpentine, &c., 

 before the antennas were cut off, now showed no repugnance 

 at all in the presence of these compounds. It was also found 

 that when the antennee were removed the insects did not rush 

 to food. 



The author has entirely confirmed Hauser s investigations ; 

 and there is no doubt that in the antennse of these animals, 

 there resides the sense of olfaction ; but it should be borne in 

 mind that the antennae are also tactile organs — i.e., they have a 

 dual function. 



The sense of hearing is somewhat well developed in the 

 Iiiscdii* " The only organs which can safely be regarded as 

 auditory in insects, are those which occur in grasshoppers 

 { Acrid idiv), crickets (Achctidn), and locusts (^Locudida:), and 

 which were first accurately described by Von Siebold. They 

 have since been studied by Leydig, Hensen, Ranke, and Oscar 

 Schmidt, but it must be confessed that much obscurity still 

 hangs over their minute structure. In the Acrididce, the 

 chitinous cuticula of the metathorax presents on each side, 

 alcove the articulation of the last pair of legs, a thin tympani- 

 form membranous sjDace surrounded by a raised rim. On its 

 inner face, the cuticular layer of the tympaniform membrane 

 is produced into two processes, one of which is a slender stem 

 ending in a hollow triangular dilatation. A large tracheal 

 vesicle lies over the tympanic membrane, and between its 

 wall and the latter, a nerve derived from the metathoracic 



* The weevils [Sitona crinita and Sitona llneata), which feed upon the 

 leaves of beans and jieas, are very sensitive to sound, and if approached 

 1 hey usually drop from the leaves to the ground. (See Dr. Grifliths' The 

 Jiiseases of Cropx, p. 26.) 



