SENSES OF INSECTS. 325 



The antennae are, in the locust, organs of smell, The 

 palpi are probably only organs of touch. It has been shown 

 by F. Will that wasps have the sense of taste, and that 

 minute gustatory organs are placed near the mouth. These 

 organs, in the shape either of pits or projecting bulbs, in 

 connection with peculiar nerve-endings, are situated on the 

 labium, paraglossae, and on the inner side of the maxillae. 

 Similar organs occur in ants. 



Pig. 284. Longitudinal section of the facetted eye of asphinx: the eye-capsule or 

 sclefa facetted externally (/), and sieve-like within, shows the rod-like ending of the 

 optic nerve-fibres ; k, layer of the crystalline lens; i, iris-like-pigment zone; ch, 

 choroid composed of pigment cells ; sn, optic nerve ; tr, trachea lost in line bandies 

 of fibrillffi. After Leydig, from Graber. 



The ears are well developed in the locust, and we know 

 that the sense of hearing must be delicate, not only from the 

 fact that a loud alarum with kettles and pans affects them, 

 but the movements of persons walking through the grass 

 invariably disturb them. Besides this, they produce a fid- 

 dling or stridulating sound by rubbing their hind legs 

 against their folded wing-covers, and this noise is a sexual 



