22 RHYSSA PERSUASORIA 



The ichneumon's proceedings are as follows : 

 After alighting on the trunk of a fir-tree it runs 

 actively up and down the bole, occasionally 

 fl5dng to a short distance and settling again to 

 resume investigations. During this search the 

 insect's antennae are seen to be in a state of 

 tremulous agitation. This hunt for the Sirex 

 larva is an all-important matter, for on its 

 success depends the continuity of the ichneu- 

 mon race. Persuasoria, however, is equal to 

 the situation. Presently she is seen to come 

 to a standstill, and drawing up her legs plants 

 herself firmly on the surface of the bark. In 

 this posture she remains motionless with the 

 exception of the antennae which continue to 

 beat the air. Now the ovipositor is directed 

 backwards and bent round and over in a 

 circular form until the extreme point rests on 

 a spot immediately below the creature's 

 abdomen. A drilling operation is then effected 

 with the naked ovipositor, which, held in posi- 

 tion by the tip of the sheath, begins to pene- 

 trate the wood, whilst the sheath, unaltered, 

 preserves its curved form. The purpose of the 

 divided sheath is now apparent, for as the ovi- 

 positor (drill) sinks deeper into the substance 

 of the wood, its upper portion is seen to come 

 away in loop-fashion from between the hair- 

 hke sections, and by degrees the whole length 



