SEGMENTA TION. 



35 



Although it is convenient to speak of the head as the first 

 segment, it represents the three first post-oral metameres of 

 the embyro. I regard Newport's segment as the last of these 

 cephalic metameres ; the second is only represented by its 

 ventral appendages, the maxillae, which form the greater part 

 of the head of this larva ; and no traces of the first cephalic 

 metamere can be distinguished externally, at least. 



Adopting these views, the first thoracic segment is the fourth 

 post-oral metamere, and is so numbered in my figures. The 

 three cephalic, three thoracic, and nine abdominal segments, 

 counting the last obvious segment as two, give fifteen post-oral 

 somites, of which the first is apparently suppressed. And the 

 second is only represented by its ventral appendages, the 

 maxillae. Formerly two pre-oral somites were added, making 

 seventeen, a number which has usually been regarded as typical 

 of all insects except the Orthoptera, which generally exhibit 

 eleven abdominal segments. 



The question as to the morphology of Newport's segment is 

 one of considerable interest, and will be further discussed here- 

 after. The compound nature of the last segment is not, I 

 think, doubtful, but is manifested by the existence of a pair 

 of ventral appendages close to the anus, each consisting of 

 three joints, with a small ventral plate in front of them 

 (Fig. 4, d and e). The concave disc, which contains the 

 posterior spiracles, is fringed with papillae, of which four are 

 large and eight smaller ; five are situated on each side, and two 

 below. 



2. THE INTEGUMENT. 



The Integument is thick and leather-like in the adult larva ; 

 its cuticular portion consists of two distinct parts : the epiostra- 

 cum and the endostracum. 



The Epiostracum forms a continuous layer over the whole ex- 

 ternal surface, and is inflected into the mouth, anus, and 

 spiracles. It forms the solid recurved spines on the anterior 

 portion of the segments, and the muscles are inserted into it 



3—2 



