56 INSECT TRANSFORMATIONS. 



dious intrusion of a common ichneumon fly (Pimpla 

 manifestator, GRAVENHORST), easily known by its 

 being black, with the legs red. This ichneumon 

 sometimes 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 young one, closes up the doorway with a bar- 

 ricade of kneaded clay. It is this very barricade 

 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 of those as the saw-flies or 

 the tree-hoppers (Cicadce.) 



The ovipositor of all the true ichneumons (Ich- 

 neumonidce) 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. manifestator) will be sufficient to 

 give the reader a distinct notion of the others 

 Being 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- 



