4 INTBODUCTION. 



The corresponding ventral plates form the pro-, meso- and 

 metasUrna. 



The prosternum is a longitudinal plate, generally more or less 

 parallel-sided, with a ccmstriction near the base, but occasionally 

 angustate or narrowed posteriorly ; this constriction admits the 

 insertion of the anterior pair of legs. 



The mesosternmn is a plate of irregular outline, usually about as 

 broad as long, with sinuate sides to admit the middle pair of legs ; 

 the hinder margin extends somewhat beyond the middle coxae, 

 and is truncate, or more or less rounded ; the relative width 

 of this intercoxal portion is the expression of the breadth or 

 slenderness of the insect. 



Wings. 



Glandular folds or 

 stink-glands. 



Abdomen. •-' 



First tarsal segment. ' 



Second tarsal segment. '' 



T hird tarsal segment. -- 



Pulvillus. -- 



Claws. - 



Antenna. 

 Frons. 



Frontal suture. 

 Occiput. 

 Median suture. 



Prozona. 



Suture. 



Metazona. 



Shoulder. 



Scutellum. 



Sutural margin. 



Costal margin. 



Posterior margin. 



Posterior femur. 



Posterior tibia. 



Posterior tarsus. 



Last dorsal segment. 

 Pygidium. 



Forceps. 



Fig. 1. — Diagram of dorsal aspect of an Earwig. 



The metasternum is of the same general shape as the meso- 

 sternum, but is larger, in order to carry the hinder or largest 

 pair of legs ; its maximum breadth is in the anterior portion, and 

 it is strongly narrowed behind by the emargination of the sides 

 so that the posterior portion forms a relatively narrow lobe which 

 generally extends beyond the coxae ; the shape of this lobe affords 

 useful characters : its posterior margin may be truncate, sinuate 



