— 54 — 



(paraptera) are popularly considered to be the modified* 

 fore wings. 



METATHORAX. 



Dorsal aspect. — When the elytra are closed the meta- 

 notum is completely covered and invisible. By removal of 

 the elytra, the metanotum is revealed as a narrow transversal 

 bar, on the surface of which a number of sutures and ele- 

 vated and depressed lines are to be seen. The work of dis- 

 tinguishing the various component sclerites of the metano- 

 tum cannot be done satisfactorily by the elementary student. 

 There is a conspicuous depression or groove extending cau- 

 do-cephalad along the dorsimeson, with strongly chitinized 

 margins, which project slightly mesad over the depression. 

 On the inner surface of the elytra, near the base of the mesal 

 margins, there are two, slight, projecting processes. These 

 small processes have strong, acute margins, which project 

 slightly laterad. When the elytra are closed, the raised pro- 

 cesses fit into the groove of the metanotum, and the laterad- 

 projecting margins of the processes lie under the mesad-pro- 

 jecting margins of the groove, the whole structure forming 

 a means for the firm holding of the elytra over the dorsum 

 of the body. The firm holding of the elytra is further aided 

 by the inflexed lateral margins and by the close dovetailing 

 of the mesal margins along the dorsimeson. 



Ventral aspect. — As in the other thoracic segments this 

 includes both the sternum and the pleural sclerites. 



Metasternum. — The metasternum is, as the mesosternum, 

 best described as saddle-shaped. It has a rather broad, blunt 

 tongue, projecting cephalad between the mesocoxseto meet the 

 caudad-projecting tongue of the mesosternum. It presents, 

 also, an acute-angled process, projecting caudad between the 



*The homology of the elytra with the paraptera and not with the fore wings of 

 other insects was first pointed out by F. Meinert in 1880. In Dyliscus and in many 

 other beetles rudiments of the forewing exist beneath the elytra. 



