THE FIRST PAPER-MAKER 



175 



f.B. 



On top you see the back portion of the front 

 wing, with a curved groove on its inner edge. 

 Below, you get the front portion of the hinder 

 wing, with a series of little hooks, microscopic, 

 yet exquisitely moulded, which catch into the 

 groove on the opposite portion. When thus 

 hooked together, the two wings on the right act 

 exactly like one. So do the two 

 on the left. But they can be un- 

 hooked and folded back on the 

 body at the will of the insect. 

 To either side of No. 13 you will 

 notice sections of the two wings, 

 which will help you to under- 

 stand the nature of the mechan- 

 ism. On the right, the wings are 

 seen hooked together ; on the left, 

 they are caught just in the act 

 of unhooking. 



Last of all, and most important 

 of all to ordinary humanity, we 

 come to the sting, with its append- 

 age the poison-bag. It is well NO. H.-POISON BAG, 



. SHEATH, DARTS, 



represented in No. 14. The main ANI) PALPI . 

 object of the sting, and its ori- 

 ginal function by descent, is that of laying eggs ; 

 it is merely the ovipositor. But besides the grooved 

 sheath or egg-layer (marked S in the illustration) 

 and the two very sharp lances or darts (marked D) 

 which pierce the flesh of the enemy, it is provided 

 with a gland which secretes that most unpleasant 

 body, formic acid ; and when the wasp has cause 



