PLATE II— continued. 



and 15) and Uzel, the lingua arises between the maxillse, and the super- 

 lingua between the maxilte and the mandibles. Therefore, it is more 

 probable that the first of these four pairs of ganglia (fig. 16, 1-i) be- 

 longs to the mandibular segment and that the second pair are the homo- 

 logues of the superlingual ganglia. 



Fig. 17. — Diagrams of the Elements of the Head. 



(After Comstoek and Kochi. ) 



A. — Lateral aspect. 



B. — Ventral aspect. 



To illustrate the morphological relations of the arrangement of seg- 

 ments of the head, they are represented as distinct, of uniform size, and 

 in a direct line: 



First. Outline of segments made. 



Second. Longitudinal line representing line of separation of sternal 

 and pleural elements of segments. 



Third. Chain of ganglia added, 1 pair for each segment. 



Fourth. Compound eyes and the ocelli were represented in the first 

 segment because innervated by the protocerebrum. 



Fifth. Position of the appendages indicated, a pair to each segment 

 except first. Antennae to second segment because innervated by deuto- 

 cerebrum. 



Sixth. Mouth represented as opening in ventral wall of third seg- 

 ment. 



Fig. 18. — Ventral Aspect of the Metathorax of a Nymph of Pteronarcys. 

 (After Comstoek and Kochi.) 



Fig. 19. — Ventral Aspect of the Metathorax of Stenopelmatus. 



(After Comstoek and Kochi.) 



The position of the furca within the body is represented by a dotted 

 line. 



A typical segment is composed of : a ventral part, sternite ; two lateral 

 parts, pleurites ; and a dorsal part, tergite. 



Each thoracic segment is composed of two subsegments. The line 

 separating these subsegments passes, on the pleural aspect, between the 

 episternum and the epimeron ; and on the tergal aspect, between the 

 scutum and scutellum. The division on the sternal aspect is not so easily 

 recognized, but it is clearly evident in the nymphs of Pteronarcys and 

 Stenopelmatus. (Figs. 18 and 19, s and s2.) 



The invaginations forming the furca lie in the suture between the two 

 sclerites, and are therefore a landmark for determining the division 

 between them. 



Fig. 20. — Ventral Aspect of the Meso- and Meta-thorax of Gryllus. 

 The position of the furcas within the body are indicated by dotted lines. 



