THE ABDOMEN. 35 



beetles, by the wing-cases, it is softer and more flexi- 

 ble than the belly ; in other cases the reverse. 



In beetles, and some other insects, the abdomen is 

 joined to the corselet without any joint to permit 

 motion ; while in bees, wasps, and most two- winged 

 flies, there is a very obvious joint, consisting of a 

 hinge, scooped out in the first ring for the purpose of 

 receiving a projecting part of the fourth piece of the 

 hind-back plate of the corselet, arising from between 

 the thigh sockets of the third pair of legs. 



The termination of the hind back plate ; a, joint of the abdo- 

 men j b, b, sockets of the thighs of the hind legs. 



There is besides, in the corselet, a distinct opening 

 or hole, (of a triangular form in bees), to give passage 

 to the broad tendon ( l ) of a muscle from the abdomen, 

 and to serve as a pulley ( 2 ), over which it may play. In 

 proportion as this muscle contracts, it accordingly pulls 

 the abdomen upwards, which falls downwards again 

 when it is relaxed. 



Wasps, bees, earwigs, and many other species, have 

 the power of moving the abdomen in various direc- 

 tions, as a whole, and of bending and curving it as 

 a dog does his tail, all of which motions are performed 

 by means of muscles attached to the inner surface of 

 the rings. 



The muscles or cords by which every motion is 

 performed are very numerous, as may be seen from 



(1) In Latin, Funiculus, 



(2) In Latin, Trochlea. 



c2 



