ICHNEUMON FLIES.* 



Under this popular designation may be included several 

 thousand allied species of insects, examples of which are shown 

 on Plate I., Figs. 6, 7, 8 and 9. They are not flies in the 

 zoological sense, but are all close relations of the bees and wasps, 

 albeit not necessarily like them in appearance. They range in 

 size from extremely minute insects, hardly visible to the naked 

 eye, up to as long or even longer than the Hornet, though less 

 heavily built. They have jaws, long antennae, and four wings, 

 which are always carried along the back and are small in propor- 

 tion to the creature with few ribs in the supporting framework. 

 In habit they are very active and energetic. Ichneumons probably 

 comprise (with the possible exception of adverse weather condi- 

 tions) the most potent of all the forces operating to keep in 

 check an overwhelming increase in other insects a misfortune 

 which always threatens. They do not achieve this by devouring 

 them outright as the Ladybird does, but are parasitic and lay 

 their eggs in or upon the insects they attack. The Ichneumon 

 grubs then feed upon the juices of their victims and come to 

 maturity in their stead. Practically all the other orders of 

 insects are laid under contribution. It would be quite impossible 

 to enter here fully into the immense activities of Ichneumon 

 Flies ; suffice it to say that most of the grubs and caterpillars 

 that destroy cultivated crops are known to be attacked. The 

 dried skins of Aphides containing the parasitic grub and forming 

 a covering for it, can always be found in considerable numbers. 

 In fact, practically all the more serious pests are destroyed by 

 Ichneumons. 



Unlike the Ladybirds and Lace wings, of which the grubs 

 are too frequently destroyed in ignorance, the large group of 

 parasitic insects here called Ichneumon Flies need no special 

 plea for their preservation, for in the early stages they are out 

 of sight or not prominently noticeable, and as adults are active, 

 watchful and able to take care of themselves. 



Description and Life History. The Eggs are deposited in or 

 upon (usually in) the bodies of other insects by means of a 

 special egg-laying apparatus. It is usually the egg, grub or 

 pupa stage which is attacked. 



The Grub, with a few exceptions, is a whitish, legless maggot, 

 like its cousin the wasp-grub in appearance but differing in size 

 according to the species. In the case of the internal feeders, 

 it lives on the juices of its prey which it eventually destroys, 

 but not before it has itself become full-fed. In some cases, it 

 leaves its prey and spins a cocoon itself ; in others it waits until 

 its victim has spun a cocoon before killing it and then merely 



* For the purposes of this publication the designation " Ichneumon 

 Flies " is made to cover the greater part of the Hymenoptera Parasitica 

 as well as the Ichneumonidce, viz., Braconidce, Proctotrypidce, Chcdcididce, 

 <fec. 



