24 The Honey-Makers 



These hinges are at X, X, the point A ^ of Fig. II. being 

 joined to X, X, by the stiff, horny arms A^, X, on either side. 

 Certain muscles which are attached to the head as well 

 as to the proboscis by contraction depress the arms, as 

 seen at ^ ^, X, in Fig. III., and lower the point ^ ^ to ^ ^, 

 opening the hinges at X, X, and thus lowering the inner 

 sheath. This now projects below the outer, and the pro- 

 boscis has been extended to its maximum length below the 

 jaws. The final act is to lengthen the tongue to its utmost 

 by withdrawing it as far as possible from the mentum Mf. 



Thus, by means of springs or hinges or levers, as one 

 may choose to think of them, the proboscis can be quickly 

 lengthened and shortened. 



A profile view of the tongue and its motor mechanism is 

 interesting and makes the manner of lengthening the organ 

 clearer. 



The proboscis is slightly lowered, otherwise A would be 

 applied closely to the line of the head, the whole apparatus 

 would be tightly closed, and its mechanism 

 concealed. 



Corresponding to the arm ZA on either 

 side is a lower parallel arm VK, which is 

 visible only in the profile. This arm, like that 

 at ZA, is tough and horny, though very slen- 

 der, and it is evident that the parallelogram 

 ZAKV, being jointed at each angle, can, by 

 swinging on these joints, depress or elevate 

 the side AK and with it the attached inner 

 sheath and tongue. 

 But this parallelogram is divided in two at points X, S, 

 and is also movable at these points, and the parallelogram 

 ZXS V can change its relative position without changing 

 that of the parallelogram XAKS as seen in Fig. V. 



Thus, the whole proboscis is lowered the distance from 



