20 



Dorsal Part (Mesonotum and Metanotum). — The dor- 

 sal part of the mesothorax is termed the mesonotum, that of 

 the metathorax, the metanotum. Unlike the pronotum these 

 parts are confined to the dorsal aspect of the body. By cut- 

 ting away the caudal part of the pronotum as indicated above 

 and spreading the wings laterad, these parts are exposed. 

 Each consists of a nearly square area. To the lateral margins 

 of the mesonotum is articulated the first pair of wings ; and 

 to the lateral margins of the metanotum, the second pair of 

 wings. 



The sutures indicating the outlines of the sclerites, of 

 which the mesonotum and metanotum are composed, are not 

 all well defined ; there is consequently some difficulty in 

 determining the limits of the sclerites. 



In each of these segments only two of the four dorsal 

 sclerites are well developed ; these are the scutum and the 

 scutellum. The scutum occupies the cephalic half of the 

 segment, the scutellum the caudal half. The scutellum con- 

 sists of three parts : a central, shield-shaped part, which in 

 this species is closely united to the scutum ; and on each side 

 a part extending to the base of the wing. The caudal border 

 of the scutellum is thickened and is connected on each side 

 with the caudal border of the base of the wing by a cord-like 

 structure. 



Make a drawing of the mesonotum and metanotum. 

 Note. — In those insects where the prsescutum and postscutellutn 

 are well developed, they usually extend entad and are often concealed 

 within the thorax. The connection of the scutellum on each side 

 with the caudal border of the base of the wing, is an -excellent guide 

 in tracing the homology of the parts of the mesonotum and the 

 metanotum. 



Ventral Part (Mesosternum and Metasternum). — 

 On the ventral surface of the body between the legs of the 

 second thoracic segment is a large sclerite ; this is the ster- 

 num of the mesothorax or mesosternum. The cephalic 



