SENSJS8 OF INSECTS. 



345 



The antennae are, in the locust, organs of touch. The 

 palpi are not only organs of touch, but probably, as in some 

 other insects, are endowed with the sense of taste, enabling 

 the locust to discriminate between the different kinds of 

 food, and select that best adapted to suit its wants. It is 

 possible that the labial nerves send branches of special sense 

 to the tongue. 



f -, 



Fig. 289. -Longitudinal section of the facetted eye of a moth : the eye-capsnie or 

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

 optic nerve-fibres ; k, layer of the crystalline lens; i, iris-hke-pigment zone c/t, 

 choroid composed of pigment cells ; sn, optic nerve ; tr, trachea lost in fine bundles 

 of fibrillse. 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 



