22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



flow over the upper surface of the proboscis and to swell into a 

 globule in the posterior angle of the proboscis between the recurved 

 free distal parts and the basal parts of the latter. The nectar globule 

 is several times sucked back into the mouth and redischarged. Though 

 recorded observations are not specific as to the exact course of the 

 nectar around the base of the tongue, it is much to be suspected that 

 the passageways between the tongue and the paraglossae, and likewise 

 the glossal channel itself, the wall of which is eversible, serve to 

 conduct the nectar in both directions. 



The principal movements of the labium are (i) the back-and-forth 

 motion of the labium with the maxillae when the entire proboscis is 

 retracted and protracted, (2) an independent movement of the labium 

 between the maxillae, (3) individual movements of the tongue during 

 feeding, and (4) the backward flexion of the tongue and palpi when 

 the proboscis is not in use. The flexion of the tongue accompanies 

 the retraction of the proboscis, and involves a retraction of the base 

 of the ligula into the end of the prementum. Other minor movements, 

 probably depending on muscle tension, adjust the various parts to 

 their functional positions. 



The extrinsic musculature of the bee's labium consists of two pairs 

 of muscles corresponding with the anterior and the posterior labial 

 adductors of generalized insects inserted on the prementum. The 

 anterior labial muscles in the bee (fig. 7 D, //) are the longest muscles 

 of the head ; they arise on the dorsal wall of the cranium, go down- 

 ward through the head, traverse the prementum (A), and insert by 

 tendons on the distal ends of the ligular arms (A, D, h) of the pre- 

 mentum. These muscles are labial retractors of the proboscis, since 

 their contraction affects not only the labium but the maxillae as well. 

 Also they take part in the retraction of the ligula into the end of the 

 prementum (A, E), which causes the deflexion of the tongue. The 

 posterior labial muscles (D, r8) arise on the anterior ends of the 

 tentorial bars of the head and converge posteriorly to a single median 

 tendon attached on the proximal extremity of the prementum. These 

 muscles probably act as protractors of the labium by flattening the 

 angle between the postmentum and prementum, thus giving the 

 labium an independent movement between the maxillae, and in addi- 

 tion they draw the prementum toward the mouth during feeding. 

 The posterior labial muscles may, therefore, be termed protractor- 

 adductors of the labium. 



The movements of the tongue during feeding, or when the bee is 

 exploring a food source, consist of lengthwise extensions and con- 

 tractions of the organ, and lateral movements of the part projected 



