173 



from between the sixth and seventh joints dorsally. There is a won- 

 derful mascular power in the anal joints, and the ovipositor is forced back 

 until it forms a perfect coil, so that when the abdomen is stretched in a 

 straif^ht line to its utmost (Fig. 3G,c) the ovipositor within the membrane 

 makes a circle almost as large as a quarter of a dollar, the anal joint 

 having made a three-fourths turn within the membrane. In this man- 

 ner the ovipositor under the venter has been sufficiently shortened to 

 bring its tip against the bark. During this operation, however, the 

 outer sheaths, which have not followed the ovipositor within the 

 membrane, have been obliged to make a more or less irregular coil 

 opposite to and in front of the membrane on the ventral side as at 

 Fig. 36,/. Now commences the operation of boring, and with the won- 

 derful muscular i^ower in the anal joint and the elasticity of the mem- 

 brane, the insertion of the ovipositor goes on quite steadily if the wood 

 be in the least soft. As the borer enters, the sheaths make a larger 

 and larger loop on one side of the body, or even a valve on each side, 

 and at last, when the borer is well nigh inserted, they present the ap- 

 pearance represented in a and Z>. Our 

 figures, made from sketches in the 

 field at the time mentioned, will con- 

 vey a very good idea of this interest- 

 ing process. In withdrawing the 

 ovipositor the reverse action takes 

 place and the loops of the outer 

 sheaths gradually become smaller 

 and smaller; the ovii)ositor proper 

 is again forced back into the tough 

 bladder-like membrane between the 

 sixth and seventh joints dorsally and 

 we have a repetition of the appear- 

 ance (^7) as already described. The 

 popular figures of the act of oviposi- 

 tion which we have so far seen are 

 for the most part imaginary and er- 

 roneous. That of Khyssa by Blan- 

 chard, for instance, is purely imagi- 

 nary and shows the ovipositor insert- 

 ed in a Sirex larva, while that by 

 Wood is still poorer. The best we 

 have seen, and evidently copied 

 from some European work, we take 

 from an old American Agriculturist (Fig. 37). The species is evi- 

 dently Rhyssa persuasoria, which is common to Europe and North 

 America, and which, having a relatively shorter ovipositor than Tha- 

 lessa, may not require the elastic membrane. The larva and pupa of 



Fig. 37. Ehyssa persuasoria ovipositing. 

 (After the American Agriculturist). 



