14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



soft, cushionlike lobe arising mesad of the base of the galea, and a 

 very small, 2-segmented, lateral palpus (MxPlp). A V-shaped 

 sclerite, known as the loritm (Lr), which holds the basal plate of the 

 labium in its apical angle, has its arms articulated with the distal 

 ends of the maxillary cardines. 



Each maxilla is provided with four extrinsic muscles arising within 

 the head (fig. 4 A), one inserted on the cardo (10) ; the other three 

 (ji, 12, /j) on the stipes. The single cardinal muscle (/o) is the 

 usual promoter of the maxilla, which in generalized insects arises 

 dorsally on the head wall and is inserted on the cardo anterior to the 

 cranial articulation of the latter. In the bee, however, this muscle 

 arises posteriorly on the postgenal inflection at the side of the 

 proboscis fossa (fig. i C, Pge), and is inserted on a short lever arm 

 of the cardo that projects above the articular condyle (fig. 4 A). By 

 this shift in its point of origin the cardinal muscle becomes an eflfective 

 protractor of the maxilla. The movement of the two maxillary 

 cardines, however, affects both the maxillae and the labium because 

 the three appendages are yoked at their bases by the V-shaped lorum 

 (fig. 3 A, Lr). The muscles of the cardines in the bee, therefore, are 

 cardinal protractors of the proboscis. 



The long stipital muscles of the maxilla (fig. 4 A, 11, 12, /j) are 

 the primitive adductors, or functionally, protractors of a generalized 

 maxillary appendage, that arise on the tentorium. In the bee these 

 muscles have their origins on the extreme anterior ends of the longi- 

 tudinal tentorial bars {AT), and hence at first sight appear to arise 

 on the facial wall of the head. In most insects the stipital muscles act 

 as protractors of the maxilla because their mesal pull (adduction) 

 flattens the angulation between the cardo and the stipes and in this 

 way protracts the appendage. The muscles evidently produce the 

 same action in the bee, and become stipital protractors of the 

 proboscis. Though the slant of the muscles in the fully protracted 

 condition of the maxilla might suggest that the stipital muscles now 

 become retractors, it is probable that the retraction of the proboscis 

 is effected principally by the long cranial muscles of the labium (fig. 

 7A, D, 17). 



The tapering bladelike galea of the maxilla is attached to the stipes 

 by a prolongation of its base that forms a triangular plate, or subgalea 

 (fig. 4D, G, Sga), implanted laterally on the anterior surface of the 

 distal end of the stipes. From the subgalea a strong midrib runs 

 through the length of the galea to its tip. In the functional, protracted 

 position of the proboscis the galeal blade extends straight out from 



