PHYSIOLOGY OF INSECTS. 113 



horny plate, corresponding in character with the 

 upper lip : its variations in form are of great 

 assistance to entomologists, in determining to 

 which kind any insect belongs. 



397. The third portion of the lip (palpiger) 

 appears mostly to rise from behind the second 

 part, but not unfrequently is continuous with it, 

 and separated only by a sutural line ; it is usually 

 smaller, and of softer substance than the second 

 part, and it invariably is to be distinguished by 

 bearing the feelers. 



398. The labial feelers (labipalpi) originate one 

 on each side of the palpiger, from which they con- 

 tinue divaricating : these are composed of several 

 distinct joints, of which the terminal one varies 

 much in form. 



399. The terminal portion of the lip (ligula) is 

 always more soft and fleshy than either of the 

 preceding parts : it is remarkable for the infinite 

 variety of forms which it assumes, and is the most 

 certain guide in ascertaining insects from de- 

 scription. 



400. An entire ligula (ligula Integra) is when 

 its termination is simple and undivided; an entire 

 ligula is either obtuse or acute, truncate or rotun- 

 date, elongate or abbreviated. 



401. A bifid ligula (ligula bifida) is when there 

 is a deep notch down its centre, thus making the 

 termination double : a bifid ligula is usually very 

 obtuse. 



