142 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



If the oblong plate of the model (fig. 48 A, 2Vlf) is moved simul- 

 taneously with the quadrate plate, but in the opposite direction, the 

 effect is to protract and retract the stylet in the same direction as 

 the lancet, but with each stroke the lancet moves faster and farther 

 than the stylet. Observations on the living bee, however, do not show 

 that this movement ordinarily takes place, though it seems entirely 

 possible. 



When the tip of the sting of a living bee is examined under the 

 microscope, and is not allowed to touch an object it can penetrate, only 

 one lancet (the left, in the experience of the writer) is seen to move 

 back and forth on the stylet and to be protracted beyond the latter. 

 Hence, it seems probable that as soon as the tip of the shaft is inserted 

 into the skin of the victim by the backward swing of the basal ap- 

 paratus, the left lancet must be thrust out in advance of the stylet, 

 where it holds its position in the wound by means of its barbs, and 

 that then the right lancet is forced in beyond the left. Successive al- 

 ternating thrusts of the lancets would then bury the entire sting shaft 

 deeper and deeper in the flesh in the manner commonly observed. The 

 force of the backward pull of the retractor muscles is now expended, 

 not on the retraction of the lancets, but in stretching the protractor 

 muscles, which, when thus restored to a condition of activity, give, 

 each in turn, another thrust to the lancets. The motion of the lancets 

 operates the valves attached to the dorsal margins of the lancets within 

 the cavity of the bulb of the shaft, and the valves drive the poison 

 liquid through the channel of the sting, from which it issues by way of 

 the ventral cleft between the distal ends of the lancets. 



ABBREVIATIONS USED ON THE FIGURES 



a-a, dorso-pleural line. bv, basivalvula. 



Ac, antecosta. bw, cut edge of body wall. 



AcGl, accessory gland. 



AcGlD, duct of accessory gland. 



AcGlO, opening of accessory gland. 



aiv, anterior intervalvula. 



Am, amnion. ''' ' , "7 



Coel, coelomic sac. 

 An, anus. ^ 



. , Cx, coxa. 



Ap, apodeme. ^ ^ , 



/ , , CxC, coxa! cavity. 



' CxP, pleural coxal process. 



b-b, pleuro-ventral line. D, dorsum. 



bcpx, bursa copulatrix. d-2, dorsal muscles of mesothorax. 



BGl, "alkaline" gland of bee. (/:;, dorsal muscles of metathorax. 



bib, bulbous basal part of united second dil, lateral internal dorsal muscle, 



valvulae. dim, median internal dorsal muscle. 



Bs, basisternum. dls, dilator muscle of spiracle. 



Cd, cardo. 

 Cdbl, cardioblast. 

 Cer, cercus. 

 :/, caudal filament. 



