STINGS AND OVIPOSITORS 1 003 



; sting ' is usually formed of a pair of darts, beset with barbed teeth 

 at their points, and furnished at their roots with powerful muscles, 

 whereby they can be caused to project from their sheath, which is a 

 horny case formed by the prolongation of the integument of the last 

 segment, slit into two halves, which separate to allow the protrusion 

 of the sting ; whilst the peculiar ' venom ' of the sting is due to the 

 ejection, by the same muscular action, of a poisonous liquid, from a 

 bag situated near the root of the sting, which passes down a canal 

 excavated between the darts, so as to be inserted into the puncture 

 which they make. The stings of the common bee, wasp, and hornet 

 may all be made to display this structure without much difficulty in 

 the dissection. The ' ovipositor > of such insects as deposit their 

 eggs in holes ready-made, or in soft animal or vegetable substances 

 (as is the case with the Ichneumonidce), is simply a long tube, which 

 is inclosed, like the sting, in a cleft sheath. In the gall-flies 

 (Cynipidce) the extremity of the ovipositor has a toothed edge, so 

 as to act as a kind of saw whereby harder substances may be pene- 

 trated ; and thus an aperture is made in the leaf, stalk, or bud of 

 the plant or tree infested by the particular species, in which the egg 

 is deposited, together with a drop of fluid that has a peculiarly 

 irritating effect upon the vegetable tissues, occasioning the production 

 of the ' galls,' which are new growths that serve not only to protect the 

 larvae, but also to afford them nutriment. The oak is infested by 

 several species of these insects, which deposit their eggs in different 

 parts of its fabric ; and some of the small * galls ' which are often 

 found upon the surface of oak-leaves are extremely beautiful objects 

 for the lower powers of the microscope. In the Tenthredinidce, or 

 ' saw-flies,' and in their allies, the Siricidce, the ovipositor is furnished 

 with a still more powerful apparatus for penetration, by means of 

 which some of these insects can bore into hard timber. This consists 

 of a pair of * saws ' which are not unlike the ' stings ' of bees, &c., 

 but are broader and toothed for a greater length, and are made to 

 slide along a firm piece that supports each blade, like the ' back ' of 

 a carpenter's * tenon-saw ; ' they are worked alternately (one being 

 protruded while the other is drawn back) with great rapidity ; but 

 when not in use they lie in a fissure beneath a sort of arch formed 

 by the terminal segment of the body. When a slit has been made 

 by the working of the saws they are withdrawn into this sheath ; 

 the ovipositor is then protruded from the end of the abdomen (the 

 body of the insect being curved downwards), and, being guided into 

 the slit by a pair of small hairy feelers, there deposits an egg. 1 

 Many other insects, especially of the order Diptera, have very pro- 

 longed ovipositors, by means of which they can insert their eggs 

 into the integuments of animals or into other situations in which 

 the larvae will obtain appropriate nutriment. A remarkable example 



xxv. p. 174 ; and ' Ueber Bau und Entwickelung des Stachels der Ameisen,' op. cit. 

 xxviii. p. 527. 



1 The above is the account of the process given by Mr. J. W. Gooch, who has 

 informed the Author that he has repeatedly verified the statement formerly made by 

 him (Science Gossip, Feb. 1, 1873), that the eggs are deposited, not, as originally 

 stated by Keaumur, by means of a tube formed by the coaptation of the saws, but 

 through a separate ovipositor, protruded when the saws have been withdrawn. 



