496 THE ICHNEUMON. 



rejecting the thick nervures. It makes no cocoon, but retires into the ground, excavates 

 a kind of oval cell, which it lines with a slimy substance, and there awaits its final 

 change. 



The well-known black GOOSEBERRY-FLY (Nematus grossuldricc] is another of the Saw- 

 flies. Its larva, so destructive to the fruit, is blackish gray. These tiresome creatures 

 are often seen in great numbers, more than a thousand having been taken on a single 

 gooseberry-bush, and there are two broods in the course of a year. Without going into 

 further details, it is sufficient to say that there is hardly a plant without its especial 

 Saw-fly, and that any one who can discover a really effectual mode of checking their 

 ravages will confer no slight benefit on mankind. 



THE fine insect on the same illustration, which is 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 immediately 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 perfect insects often make their appearance in houses, the larvag 

 having been concealed in the timbers and rafters ; and I know of one case where a 

 gentleman who had built a wooden garden-house, was sadly annoyed by the multitudes 

 of the Sirex which emerged from the timber. In such cases the insects do not seem to 

 attain their full dimensions, but appear dwarfed and stunted. All wood-boring insects 

 are, however, extremely variable in size. 



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 

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

 tube. 



The first family is that of the Cynipidag, 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 well-known Bedeguar of the 

 rose, with its soft mossy envelope and delicate green color, relieved by bright pink, is 

 caused by one of these insects (Cynips rosai) ; and the celebrated Dead Sea-apples are 

 nothing but galls formed by the Cynips insdna. The spherical oak-galls, which contain 

 a single insect, and are about the size of a large marble, are closely allied to the true 

 Ink-galls ; and if one of these objects be cut with a knife, the action of the astringent 

 juice upon the iron of the blade will produce a kind of ink. The best galls are those 

 which are gathered before the insect makes its escape, as the astringent quality is then 

 more powerful. 



The true Ichneumons, of which a specimen is given in the illustration, form a vast 

 group of insects, the British Ichneumonidas alone numbering many more than a thousand 

 described and acknowledged species. In them the ovipositor is straight, and is em- 

 ployed 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 bradawl. 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 entomologists always find that when 

 they attempt to rear insects from the egg or the larval state, they must count upon 

 losing a very large percentage by the Ichneumons. 



Take, for example, three or four caterpillars of the common white cabbage butterfly, 

 place them under water, and open the body from end to end. It will be found that, in 



