40 



AN INTRODUCTION TO ENTOMOLOGY 



dt 



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 generalized 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 tin' 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 sclerites 

 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); 

 recently they have been termed the inter seg- 

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

 siders them to be homologous with sclerites 

 found in the intersegmenta] 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). 



Fig. 50. Head of a 

 cricket, ental surface 

 of the dorsal wall. 



C. THE APPENDAGES OF THE HEAD 



Under this category are classed a pair of jointed appendages 

 tern H-d the aiiteuiKC, and the organs known collectively as the mouth- 

 parts. 



The antennae. The antennas are a pair of jointed appendages, 

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

 antennae vary greatly in form; in some insects they arc thread-like, 

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

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



Tn descriptive works names 1i;ivr 1 uvn s'.iven lo particular parts of the antenna;, 

 as follows (Fig. 51): 



The Scape.- The first or pn>\im;il segment <>f ;m antenna is called the scape (a). 

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

 segment; in such cases it is called thelmlli (a 1 ). 



