OF THE SKELETON. 149 



wing, and its apex reaches the head ; this is the mesotho- 

 racic scutum, and the plate immediately behind it is the 

 mesothoracic scutellum ; behind this are the metathoracic 

 scutum and scutellum, and still beyond these, and hidden 

 in the bend of the body, the single plate of the propodeon; 

 the letters will give the names of the abdominal segments, 

 the sting being the terminal segment or telum. On each 

 side, in front of the mesothoracic scutum, will be seen 

 a somewhat triangular piece : concerning the true character 

 of these much has been written, but it is the opinion of 

 the best insect anatomists that these plates correspond 

 with the scutum of the prothorax, shown in a more dis- 

 tinct and decided manner in the Sphex, (see page 145), 

 and as we trace the changed appearance of this part in 

 some other orders of Hymenoptera, we shall find it be- 

 coming perfectly distinct in the genera Sirex and Cephus, 

 and united to the mesothorax by an articulation, possessing 

 as great freedom of motion as that of the prothorax in 

 beetles and locusts. Immediately at the base of each 

 fore wing in the hornet, is a small tubercular plate, which 

 is usually called the tegula. 



In beetles, the structure is very simple as regards those 

 parts, the variations in which are employed by authors as 

 distinguishing characters. In the figure of Hydrophilus 

 piceiiSjSi large water beetle, placed at the head of this 

 chapter, the skeleton is divided into five parts, exhibiting 

 the inferior or sternal portion of the insect j B is the under 

 side of the head ; D D the sternal surface of the protho- 

 rax, properly described as the prosternum ; F F is the 

 sternum of the mesothorax, this is properly described as 

 the mesosternum ; and H H is the sternum of the meta- 

 thorax, and is properly described as the metasternum. 

 Nothing can possibly be more simple, or more readily im- 

 pressed on the memory, than this nomenclature. It not 



