HYMENOPTERA. -—CYNIPIDA. WAH 
rally inspecting the abdomen of the female of C. quercus folii (ig. 
73. 18.), the dorsal segments will be perceived to be deflexed and 
extended to the ventral edge of the abdomen; the venter being 
terminated by a pointed piece (fig. 18. d, fig. 20. d) having a canal 
running along its middle, which is also produced considerably be- 
yond its front margin in the shape of a spine: this is the terminal 
ventral segment of the abdomen, and the canal above mentioned is 
intended for the reception of the capillary terebra (c) and the two 
valve-like sheaths (b, b). On removing the side of the abdomen 
(fg. 73. 19.), these two sheaths are found to originate in two broad 
curved plates (b), which are in fact the basal portion of the sheaths, 
the terebra itself (c) being a long and exceedingly delicate but com- 
posite seta. Burmeister is the only author who has attempted to 
discover the parts of which this is composed, and he describes and 
figures it (Manual Transl., p. 199. pl. 23. fig. 15. 18.) as consisting 
(in addition to the two outer valves, his fig. a, a) of two external sete 
(4, 6), and one central very delicate bristle (his fig. c). It appears to 
me, however, upon a dissection of many specimens of C. quercus folii, 
that the terebra is composed, like that of Sirex, Ichneumon, Vespa, 
&c., of amore robust seta (fig. '73. c), channelled on its under side 
for the reception of two equal and very slender bristles (e, ec), which 
are slightly dilated at the base, and pushed forward along the channel 
or gutter of the central piece, by strong muscles. 
With this instrument the female insect punctures* the surface of 
leaves, buds, stalks, and young stems and roots of various plants and 
trees, increasing the aperture by the continued action of the terebra, 
which is stated to be denticulated at the extremity, and through 
which an egg is propelled into the wound of the plant, together with 
a small quantity of an irritating fluid, the action of which upon the 
plant, in some way or other, causes the production of tumours or galls 
of various sizes, shapes, and colours, the interior of which being of a 
solid substance becomes the food of the young grub when hatched. 
Various theories have been proposed as to the real formation of these 
galls, with a view to trace the means which nature employs to produce 
such very different kinds of galls upon the same tree from the wounds 
made by insects of the same genus. Hitherto, however, for want of 
direct observations, conjectures alone (some plausible enough) have 
* See Bonnet, Observ. divers sur les Insectes, tom, il. p. 257. obs. 38, 
