JULY. 189 



have thus seen that these insects attack the larvse of Hyme- 

 nopterous, Dipterous, and Homopterous insects, in the case 

 of Wild Bees, Midges, and Aphides ; other species of these 

 orders are similarly affected, as well as the Coleoptera, 

 though the greater number are appropriated to the order 

 Lepidoptera. But it does not end here, for these parasites 

 are themselves liable to the attacks of smaller species belong- 

 ing to the same family, and the instinct is remarkable, which 

 guides these second parasites to the particular caterpillars 

 already made the prey of the larger Ichneumons, which are 

 to furnish their own offspring with support. These interest- 

 ing, though diminutive insects, are divided by Latreille into 

 groups known by the number of joints in the palpi, but 

 these cannot be investigated in this rapid sketch, which is 

 only intended to excite an interest, leading to research both 

 in works of more pretension, and, better still, in the works 

 of nature, which will amply repay the student. What an 

 immense field is open to his survey may be imagined from 

 the fact that in this family alone, including merely the 

 European species, a work of three thousand pages has been 

 published by Gravenhorst. The colour and form of many 

 species are highly beautiful. 



