110 BEES AND WASPS [OH. 



softer and more vascular tissues beneath. The whole 

 apparatus consists of three long pieces actuated by a 

 complicated set of muscles and levers, and connected 



Poison 

 Studs- 



Needles 



Fig. 19. Diagrammatic cross-section of a wasp's sting in 

 the region of the letter D., in Fig. 18 



by a tube with the poison-bag. These three pieces 

 are the "director," and two three-sided "needles," 

 whose opposed sides are concave, and which bear six 



p-g 



Fig. 20. Optical section of tip of a needle from the sting of Vespa 



germanica ? . Highly magnified 

 &., barbs, jp.c., poison canals perforating bases of barbs, p.g. , poison 



channel running along inner face of needle, cf. Fig. 19. Actual 



length of the part figured 0'37 mm., breadth at widest part 



0*05 mm. 



barb-hooks at their apices. The "director" is sharply- 

 pointed posteriorly and is rounded on its upper sur- 

 face ; while on its lower face is a deep groove in which 



