314 
SYSTEMATIC ARRANGEMENT 
JOPPA PICTA. 
Plate XXXI. Fig. 3. 
This and the species delineated on the following 
plate, afford examples of the very extensive family 
of the Ichneumonidae, whose economy is so remark- 
able. They deposit their eggs in the bodies of other 
insects, particularly caterpillars, which are there 
hatched, and the young feed on the entrails of the 
unfortunate victim. To enable them to convey their 
eggs into holes and fissures where caterpillars or 
pupae often lurk, they are generally provided with a 
long ovipositor, which is usually very slender, and 
too weak to pierce the skin of the hand, although 
the insects often make the attempt when seized. 
As this weapon generally appears tripartite, these 
insects were formerly named Muscce tripiles, and, 
from their habit of vibrating their antennae, Muscce 
vibrantes. They may, in general, be known by their 
narrow elongated form, attenuated, and, in most 
cases, petiolated abdomen, with its liair-like appen- 
dages behind, and long many-jointed antennae, which 
are often recurved and annulated. The Ichneumon id® 
are a very numerous tribe, no fewer than 1300 
European species having been described by Graven- 
horst in his monograph of this family, and of these 
a large proportion occur in Britain. Our British 
species, however, have not yet been carefully inves- 
tigated, and it is much to be desired that some com- 
petent observer would undertake the task. These 
insects perform an essential service by destroying so 
