56 INSECT TRANSFORMATIONS. 



dious intrusion of a common ichneumon-fly (Pimpla 

 manifestator, G raven horst), easily known by its be- 

 ing black, with the legs red. This ichneumon some- 

 times pays a visit to the nest of the wasp before it is 

 completed, for Reaumur has seen one peep into the 

 entrance and then start back as if afraid of its 

 depth ; but, for the most part, she waits patiently till 

 the wasp, having laid in a store of caterpillars for 

 the yomig one, closes up the doorway with a bar- 

 ricado of kneaded clay. It is this very barricado 

 which the ichneumon determines to assail in order to 

 find a nest ready prepared and stocked with provi- 

 sions for her own progeny. With this design she 

 makes use of her ovipositor, which is as admirably 

 adapted to the purpose as those of the saw flies or 

 the tree-hoppers {CicadcB). 



The ovipositor of all the true ichneumons {Ich- 

 nemnonidce) is similarly constructed, consisting of a 

 borer enclosed in a sheath, which opens through its 

 whole length like the legs of a pair of compasses. It 

 is longer or shorter, and stronger or more slender, 

 according to the substances which it may be neces- 

 sary to penetrate when the eggs are deposited. The 

 description, therefore, of the ovipositor of the one 

 just alluded to (P. incniifesiator) will be sufficient to 

 give the reader a distinct notion of the others. 

 l?eing intended to penetrate into the deep holes dug 

 by mason-wasps, the ovipositor of this insect is 

 nearly three inches long, and, as it is not concealed 

 in the body like those of gall-flies, it appears like a 

 tail formed of a long black bristle. On examining 

 this a little more narrowly, we find that what 

 appears to be a single bristle is in reality three, two 

 side ones forming a sheath, and the middle one a 

 borer or brad-awl for piercing the clay barricado of 

 the mason-wasp's nest. The termination of the 

 borer is not, however, smooth, like that of a brad- 



