30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



and their muscles is present in the drones and the queen of the 

 honey bee, and also in other Hymenoptera that do not have food 

 glands. 



The sucking pump. — The organ by which the bee draws liquids 

 through the closed canal of the proboscis and into the mouth and 

 passes them on to the oesophagus is a large sack with strongly 

 muscular walls lying in the head. This sack, the sucking pump (fig. 

 10 C), extends from the mouth upward and posteriorly (A) to the 

 level of the foramen magnum, where its narrowed upper end rests 

 on the tentorial bridge {TB) and passes into the slender oesophagus 

 {Oe), which goes posteriorly through the foramen. 



The sacklike sucking pump (fig. 10 A, C), though its outlines are 

 continuous, is differentiated by structural features into two parts, a 

 larger upper part (A, Phy) ensheathed in circular muscle fibers, 

 and a smaller lower part {Ch) with a strong musculature of dilator 

 and compressor fibers on its anterior wall (C). The upper part 

 unquestionably is the pharynx: the frontal ganglion (A, FrGng) 

 lies against the lower part of its anterior wall, the arms of the oral 

 plate {y) traverse its lateral walls, its dilator muscles (dlphy) arise 

 on the frontal region of the cranium and are inserted above the 

 frontal-ganglion connectives — all of which characters, together with 

 the ensheathment by circular muscle fibers, are diagnostic of the 

 pharynx. The lower part of the organ (A, Cb) has five pairs of 

 large bundles of dilator muscle fibers attached on its anterior wall 

 (C, ^(5-jo), and these muscles arise on the clypeus. This part of the 

 pump, therefore, must be derived from the cibarium of generalized 

 insects, which is a pocket of the preoral cavity between the under 

 surface of the clypeus and the base of the hypopharynx. The hypo- 

 pharyngeal floor of the cibarial section of the pump in the bee is 

 represented by the oral plate (opl). In addition to the dilator muscles 

 the cibarium is provided with thick bands of compressor fibers (C, 

 J/) running obliquely between the dilator bundles from the side of 

 the oral plate to the median area of the anterior wall, where they turn 

 dorsally. In addition a strong anteriormost group of compressor 

 fibers arches over the mouth. In Hymenoptera, therefore, the sucking 

 pump is a cibario-pharyngeal structure ; in Hemiptera and Diptera 

 the pump is purely cibarial. 



The capacious pharyngeal section of the pump has no effective 

 dilator apparatus, since only three pairs of small muscles (fig. lo C, 

 34' 35 J J^) attach on it from the head wall. On its posterior surface 

 two groups of long slender fibers (38), arising laterally on the ten- 

 torial bridge (TB), spread downward, going beneath the circular 



