STINGS AND OVIPOSITORS OF HTMENOPTERA. 579 



whereby harder substances may be penetrated ; 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 larvee, but also to afford them nutriment. The Oak is in- 

 fested by several species of thes4 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. It is in the Tenthredinidce, or Saw-flies, and in their 

 allies the Siricidce, that the ovipositor is furnished with the most 

 powerful apparatus for penetration ; and some of these insects can 

 bore by its means into hard timber. Their " saws" are not un- 

 like the " stings" of Bees, &c., but are broader, are 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 i and when the per- 

 foration has been made, the two blades are separated enough to 

 allow the passage of the eggs between them. Many other In- 

 sects, especially of the order Diptera, have very prolonged ovi- 

 positors, 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 

 of this is furnished by the Gad-fly ( Tabanus), whose ovipositor is 

 composed of several joints, capable of being drawn together or 

 extended like those of a telescope, and is terminated by boring 

 instruments; and the egg being conveyed by its means, not 

 only into but through the integument of the Ox, so as to be im- 

 bedded in the tissue beneath, a peculiar kind of inflammation is 

 set up there, which (as in the analogous case of the -gall-fly) 

 forms a nidus appropriate both to the protection and to the nutri- 

 tion of the larva. Other Insects which deposit their eggs in the 

 ground, such as the Locusts, have their ovipositors so shaped as 

 to answer for digging holes for their reception. The preparations 

 which serve to display the foregoing parts, are best seen when 

 mounted in balsam ; save in the case of the muscles and poison- 

 apparatus of the sting, which are better preserved in weak spirit 

 or Goadby's solution. 



399. The sexual organs of Insects furnish numerous objects of 

 extreme interest to the Anatomist and Physiologist ; but as an 

 account of them would be unsuitable to the present work, a re- 

 ference to a copious source of information respecting one of their 

 most curious features, and to a list of the species that afford good 

 illustrations, must here suffice.' The Uggs of many Insects are 



' See the Memoirs of M. Laoaze-Duthiers " Sur I'armure g^nitale des Insectes," in 

 '!Ann. des Soi. Nat." Sifeme S^r. torn, xii, xiv, xvii, xviii, xix: and M. Ch. Robin's 



