142 PHYSIOLOGY OF INSECTS. 



scientifically to investigate the subject, and is very unim- 

 portant in acquiring a general knowledge of the structure of 

 insects. The prothorax bears a pair of legs, which are 

 called fore legs or propedes; they are attached to its infe- 

 rior surface, and are so articulated to the prothorax as to 

 possess the most perfect freedom in all their movements. 

 The articulation also of the head and prothorax is one 

 which permits the head to move with freedom in every 

 direction. 



The third segment is the mesothorax ; it is that large 

 and prominent part so conspicuous in butterflies, bees, and 

 flies : in beetles and the locust it is comparatively a narrow 

 segment, and is so articulated with the prothorax as to 

 allow that segment less freedom of motion than is possessed 

 by the head, yet in beetles it moves with very great facility 

 compared with that possessed by the following segments. 

 The mesothorax bears two wings, one of which is attached 

 to each side of it ; these are called fore wings, practice : 

 and two legs attached to its inferior surface ; these are 

 called middle legs, mesopedes, and have equal freedom with 

 those of the prothorax. 



The fourth segment is called the metathorax; it is small 

 in butterflies, flies, bees, the hornet and the Sphex, but 

 large in beetles and the locust ; it is very rarely so con- 

 spicuous in any insect as the prothorax in beetles and the 

 locust, or the mesothorax in the hornet or Sphex. The 

 metathorax bears two wings ; one of these is attached to 

 each side ; these are called the hind wings, metalae : and 

 two legs attached to its inferior surface ; these are called 

 the hind legs, metapedes. 



The order of these four segments, and the names and 

 position of the limbs which they bear, the antennae, 

 wings, and legs, should be thoroughly impressed on the 

 memory j notwithstanding the immense variety and confu- 



