40 AN INTROD UCTION TO ENTOMOLOG Y 



The trochantin of the mandible. — In some insects, as Orthoptera 

 there is a distinct sclerite between each mandible and the gena: 

 this is the trochantin of the mandible (Fig. 45, tr). 



The maxillary pleurites. — In some of the more generaHzed insects, 

 as certain cockroaches and crickets, it can be seen that each maxilla 

 is articulated at the ventral end of a pair of sclerites, between which 

 is the invagination that forms the posterior arm of the tentorium; 

 these are the maxillary pleurites; the pos- 

 terior member of this pair of sclerites can 

 be seen in the lateral view of the head of a 

 cockroach (Fig. 48, m. em). 



The cervical sclerites. — The cervical scler- 

 ites are the small sclerites found in the neck of 

 many insects. Of these there are dorsal, 

 lateral, and ventral sclerites. The cervical 

 sclerites were so named by Huxley ('78); 

 Pig_ 50.— Head of a recently they have been termed the t7i/(?r5^g- 

 cricket, ental surface mental plates by Crampton ('17), who con- 

 wa . siders them to be homologous with sclerites 



found in the intersegmental regions of the 

 thorax of some generalized insects. 



The lateral cervical sclerites have long been known as the jugular 

 sclerites {pieces jugulaires, Straus Durckheim, 1828). 



C. THE APPENDAGES OF THE HEAD 



Under this category are classed a pair of jointed appendages 

 termed the antennce, and the organs known collectively as the mouth- 

 parts. 



The antemiae. — The antennae are a pair of jointed appendages 

 articulated with the head in front of the eyes or between them. The 

 antennse vary greatly in form; in some insects they are thread-like, 

 consisting of a series of similar segments ; in others certain segments 

 are greatly modified. The thread-like form is the more generalized. 



In descriptive works names have been given to particular parts of the antennae, 

 as follows (Fig. 51): 



The Scape. — The first or proximal segment of an antenna is called the scape (a). 

 The proximal end of this segment is often subglobose, appearing like a distinct 

 segment; in such cases it is called the bulb (a'). 



