THE THORAX. 103 



can only bend upwards, but they are allowed in many cases a slight 

 inflection downwards. 



The number of the foot-joints varies from 1 to 5. As these numbers 

 are tolerably uniform in the several families, and as many insects closely 

 allied to them possess the same number of foot-joints, they have been 

 used in forming divisions in the several orders, which are thus distin- 

 guished. 



PENTAMEROUS (pentamera), when all the feet have FIVE joints. 

 CRYPTO-PENTAMEROUS (crypto-pentamera) , are those which truly 

 possess FIVE joints, but in which the penultimate is so small that it 

 can be perceived only upon the most rigid inspection, and by means of 

 a lens (Cerambyx). Kirby and Spence call this joint the ARTHRIUM. 



HETEROMEROUS (Jieteromera) , when the four anterior legs have, 

 FIVE, but the two posterior ones only FOUR joints. 



TETRAMEROUS (tetramera), when there are FOUR joints to all the 

 feet. The CRYPTO-LETRAMEROUS appear to have but THREE joints, 

 the penultimate being very small (Coccinella). 



TRIMEROUS (trimera), feet with three joints. 



DIMEROUS (dimera), feet with two joints. And lastly, 



MONOMEROUS (monomera), when the foot has but one joint. 



The different forms of the whole foot as well as of the individual 

 joints are shown at 83. 



82. 

 Forms of the Legs. 



The most simple form of the legs, in which all the joints have the 

 usual construction, and no peculiar qualities are displayed even by the 

 feet, is distinguished by the name of CURSORIOUS LEGS (pedes cursorii), 

 even in those cases where the insect is anything but a runner, and but 

 slowly moves about. The Carabi are the chief representatives of this 

 form. 



AMBULATORY (ambulator ii), are those whose feet have a broad hairy 

 sole (Lamia). 



GRESSORIOUS (gressorii), are those whose anterior pair is imperfectly 

 developed, whilst the rest are formed upon the type of the cursorious 

 legs. Sometimes the foot is wholly wanting (AteucTius, Lonchophorus, 

 PI. XVI. f. 2) ; sometimes all its joints are small and imperfect ( Vanessa, 

 Hipparchia, PI. XVI. f. 3). 



NATATORIOUS (natatorii), are the legs of insects which live entirely, 



