74 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 8l 



THE FIRST MAXILLAE 



The leading features of the first maxilla have been sufficiently 

 noted in the description of a generalized gnathal appendage (page 

 60) based on the maxilla of Penplancta (fig. 25). In none of the 

 other arthropods are the maxillary appendages so highly developed as 

 in the insects, but, in all the arthropods, it appears that the mandible 

 has been evolved from an appendage that was originally very similar 



Cd e 



PcR' 



Ga 



A 



B 



Fig. 30. — Maxilla of Heterojapyx gallardi. 



A, left maxilla, posterior (ventral) surface. B, right maxilla and muscles, 

 anterior (dorsal) view. 



Cd. cardo ; c. articulation of cardo with cranium; ftia, flexor of galea; flee. 

 cranial flexor of lacinia ; flcs. stipital flexor of lacinia ; Ga, galea ; HA, liypo- 

 pharyngeal apophysis ; HS, rudiment of suspensorial arm of hypopharynx ; /, 

 promotor of cardo ; KLcd, adductors of cardo ; KLst, adductors of stipes ; Lc, 

 lacinia; OQ, muscle of base of palpus; p. muscle of terminal segment of palpus; 

 PcR, posterior cranial ridge; Pip, palpus; iplp. first segment of palpus; St. 

 stipes ; u, line of internal ridge of stipes. 



to the generalized insect maxilla. In many of the higher insects the 

 maxillae, too, have become specialized, always in adaptation to special 

 modes of feeding, but a description of the modifications involved is 

 beyond the scope of the present paper. The musculature of the organ 

 is essentially the same in all groups of biting insects, except as it 

 suffers a reduction where the appendages become reduced or united 

 with the labium. 



The maxilla of Japyx { fig. 30) presents a more generalized con- 

 dition in its relation to the head than does the maxilla of the roach, 



