THE GIANT ICHNEUMON. 633 



groove it rapidly increases in size, obtaining twice its former dimen- 

 sions. 



In the genus Cimbex the larvae possess twenty-two feet, and have the 

 power of discharging a translucent greenish fluid from certain pores 

 placed on the sides of the body just above the spiracles. This feat they 

 can repeat six or seven times in succession. When they have eaten 

 their way to the next stage of existence, they spin a cocoon of a 

 brownish color and of a stringy, tough consistency, and either suspend 

 it to the branches of the tree on which they have been feeding or hide 

 it under fallen leaves. In this cocoon they remain for a comparatively 

 short time, and then emerge as perfect insects. 



The fine insect known by the name of the Giant Ichneumon is an 

 example of the next family, in which the ovipositor is converted into 

 a gimlet instead of a double saw. With this powerful instrument the 

 female is enabled to drill holes into living timber for the purpose of 

 depositing the eggs. When they are hatched the young grubs imme- 

 diately begin to gnaw their way through the wood, boring it in every 

 direction and making burrows of no mean size. Those of the present 

 species prefer fir and pine, and I have had specimens of the wood sent 

 to me which have been riddled by the grubs until they looked as if 

 they had harbored a colony of the ship-worm. 



The next group of the Terebrantia is called Entomophaga, or Insect- 

 eaters, because the greater number of them are parasitic upon other 

 insects, just as the saw-flies are parasitic upon vegetables. In these 

 insects the ovipositor is furnished with two delicate spiculte, and the 

 last segments of the abdomen are not formed into a telescope-like 

 tube. 



The first family is that of the Cynipidse, or Gall Insects, the creatures 

 by whose means are produced the well-known galls upon various trees, 

 the so-called oak-apple being perhaps the best known, and the ink-gall 

 (also found on the oak) the most valuable. These galls are formed by 

 the deposition of an egg in the leaf, branch, stem, twig, or even root, 

 of the plant, and its consequent growth. 



The true Ichneumons form a vast group of insects, the British Ich- 

 neumonidse alone numbering many more than a thousand described 

 and acknowledged species. In them the ovipositor is straight, and is 

 employed in inserting the eggs into the bodies of other insects, mostly 

 in their larval state. In some cases this slender and apparently feeble 

 instrument is able to pierce through solid wood, and is insinuated by 

 a movement exactly like that which is employed by a carpenter when 

 using a brad-awl. When not engaged in this work, the ovipositor is 

 protected by two slender sheaths that enclose it on either side. 



Were it not for the Ichneumons, our fields and gardens would be 

 hopelessly ravaged by caterpillars and grubs of all kinds, for practical 



