THE THOKAX OR TEUISTI. 51 



the same names among the vertebrates, but merely re- 

 semble them in position and functions ; they may hence 

 be said to be analogous with them, but not homologous. 

 Of these parts the tarsus alone is composed of several 

 pieces or joints, which vary in number. The most 

 universal number of joints is five, and such insects are 

 termed pentamerous. In some the number of joints 

 varies in the different pairs of legs, and such are termed 

 heteromerous ; others again have four joints — tetramer- 

 ous ; three joints, trimerous ; two joints; dimerous; one 

 joint, monomerous ; or more than five joints, polymerous. 



PENTAMEROUS, OR FIVE- JOINTED TARSUS. 



The terminal or last joint of the tarsus is armed ithw 

 claws, hooks, sponge or suction desk, according to the 

 character of the surface the insect was designed to walk 

 upon. 



The remaininor details in relation to the lesfs of insects 

 which have here merely been hinted at, may be readily 

 observed with the aid of a hand magnifying glass, an 

 instrument that should always be the companion of 

 every observer of Nature. 



GNAT (CULIX riPIENs), 



