10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



depression muscles arising respectively on the dorsal and the ventral 

 wall of the scape (H, 6, 7). 



The scape of the antenna is articulated to the head by a distinct 

 basal knob (fig. 2D), which is pivoted on a small articular process, 

 the antennafer (af), arising ventrolaterally from the rim of the 

 antennal socket (F). The antenna is thus freely movable in all 

 directions except as it is limited by the socket membrane. To provide 

 for its movement four muscles arising on the concave dorsal surface 

 of the tentorial bar of the same side of the head are inserted on the 

 base of the scape (C), two above the level of the pivot and two 

 below it. 



The labrum. — The labrum of the honey bee (fig. i A, Lin) is a 

 simple, transversely elongate flap with well-sclerotized, closely ap- 

 pressed outer and inner walls, and is freely suspended from the 

 lower edge of the clypeus. It contains no compressor muscles (fig. 

 ID C, Lm), and is movable by only a single pair of extrinsic muscles 

 arising on the frontal area of the head between the antennal bases, 

 which are adductors since they are inserted by long tendons attached 

 laterally on the posterior margin of the base of the labrum. In the 

 wasps the labrum is retracted beneath the clypeus and the clypeal 

 margin forms the lower edge of the face (fig. 9E). 



The epipharynx. — In both the wasps and the bees the epipharynx 

 (figs. 9 E, 10 C, Ephy) is a preoral outgrowth of the inner, or 

 "epipharyngeal," surface of the clypeus — not of the labrum. The 

 epipharynx of the honey bee is a large, soft structure with a prominent 

 median keel and padlike lateral lobes (fig. 9 A, Ephy). It is retractile 

 by a group of divergent muscle fibers arising on the lower part of 

 the clypeus (fig. 10 C, 25). Just above and behind the base of the 

 epipharynx is the wide, oval mouth opening (figs. 9 A, 10 C, Mth) 

 that leads into the cavity of the sucking pump. The epipharynx is 

 richly provided with sense organs, but mechanically it serves, to- 

 gether with the lacinial lobes of the maxillae, to close the food channel 

 on the base of the proboscis (fig. 9 A, B). 



The mouth. — The wide aperture behind the epipharynx that leads 

 into the sucking pump (figs. 9 A, 10 A, Mth) is the mouth of the 

 bee in a functional sense, but since the anterior part of the pump 

 (fig. 10 A, Cb) represents the primitively preoral cibarium lying 

 between the clypeus and the hypopharynx, the true mouth, in a 

 morphological sense, is between the cibarial and pharyngeal sections 

 of the pump. In the Hymenoptera, therefore, as in various other 

 sucking insects, the functional mouth is a secondary constriction of 

 the food meatus between the inner face of the clypeus and the 



