390 INSECTS ABKOAD. 



however, shows that uot ouly are they identical in their parts, 

 though the structure of those parts is modified, but that the 

 double saw of the Saw Flies, the horn-like projection of the 

 Uroceridse, the long hair -like ovipositor of the ichneumon flies, 

 and the envenomed sting of the bees and wasps, are but 

 slightly modified variations of the same organ. 



It is impossible to give a full description of so complex 

 and beautifully-made a structure as the ovipositor of the 

 Hymenoptera without the aid of many illustrations, and I must 

 therefore only mention the salient points. 



As the insects are not required to cut notches into soft wood, 

 as is the case with the Saw Flies, the powerful saws are not 

 needed, and are modified into two small spiculse, in which the 

 notches or teeth are still preserved, thongh they are too small 

 for actual use. The two horny plates which strengthen the 

 saws are soldered together, so as to support the central boring 

 instrument. This is a really wonderful piece of mechanism, 

 and I may as well here repeat the description given in my 

 " Insects at Home," and taken from the ovipositor of our fine 

 English species, Urocerus (or Sirex) gigas. It is scarcely needful 

 to observe that this organ is only possessed by the female 

 insect. 



"I very strongly recommend any of my readers who may 

 obtain a female insect to disengage the actual borer from its 

 two-bladed sheath, and examine it with the aid of a microscope. 

 A half-inch object-glass will give quite sufiicient power. It is 

 straight and stiff, but elastic, as if made of steel, and, if bent, will 

 spring back to its proper form with the elasticity of a Toledo 

 rapier. In form it somewhat resembles the instrument known 

 technically as a 'rymer,' except that the edges are rounded, and 

 not square. But the borer possesses an auxiliary cutting appa- 

 ratus which places it far above the rymer in point of efficacy. 



" Even with an ordinary magnifying lens, it is easy to see that 

 the end of the borer is developed into a sharp head very much 

 resembling that of a boarding-pike, and that the outline of the 

 shaft is broken into a series of notches. The half-inch glass, 

 however, discloses a marvellous example of mechanical excel- 

 lence. The head of the borer is then seen to be armed with 

 long sharp teeth, slightly curved inwards, and acting just as 

 docs the carpenter's ordinary centre-bit. 



