20 



The Form of Insects 



these neck-plates gives support to the suggestion 

 that they should be regarded as the hinder segment 

 or segments of the head, which have not become 

 fused with the head-capsule. There is no doubt 

 that the greater part of the capsule is built up of 



Fig. i8. — Thorax of Sawfly (Piichynemat^is). I. Upper view. II. Lower view. 

 III. Side view IV. Side view with segments separated. Prothorax : a. 

 episternum ; b sternum ; c. haunch of fore-leg ; d. pronotum. Mesothorax : 

 e. prsescutum \ /. scutum \ g. scutellum ; //. postscutellum ; i. mesophragnia ; 

 j. epimeron ; /. haunch of middle-leg. Mctathorax : k. episternum ; /. 

 haunch of hind-leg ; o. epimeron ; ni. scutum, t. tegula; n. ist abdo})iinal 

 segment. From Marlatt, Bull. 3 (tech. s.) Div. Ent. U.S. Dept. Agr. 



the four front head segments, the hindmost of which 

 has the mandibles for its appendages (6). 



Fore-body. — In the Cockroach, as in all insects, 

 the fore-body (thoraxj consists of three segments, 



