HYMENOPTERA. TEREBRANTIA. 179 



exception of one or two which belong to the Evaniidse, 

 and also some very minute species. 



The Ichneumons are elegantly formed insects, com- 

 bining the appearance of lightness and of strength, and 

 with some of them, at least, the reader must be familiar. 

 The wings are large and firm, and beautifully veined, 

 forming, in the front pair, several perfect cells ; the head, 

 which is of moderate size, is set lightly on a compact 

 thorax, larger before than behind ; the abdomen, long 

 and slender, sometimes much compressed and abruptly 

 truncated, is set on by a small point, or sometimes by 

 a fine stalk at the extreme end of the thorax, between 

 the hind legs. The legs are of moderate length ; the 

 antennae are long, slender, and tapering; the ovipositor is 

 in some species short and concealed within the abdomen, 

 in others it is visible and occasionally of great length, 

 considerably exceeding that of the body. Here is a 

 structural variety which at once points to a variety of 

 habit, and accordingly we find that while some species 

 deposit their eggs within, or upon the bodies of exposed 

 and naked larvae, others, by the exercise of the powers of 

 smell, touch, or we know not what, discover the hiding- 

 place of the larvae most carefully concealed from sight 

 and guarded from danger, and with their long oviposi- 

 tors succeed in lodging their eggs within the bodies of 

 the victims. Thus do some species penetrate to the 

 little grub within the heart of the oak-gall ; others find 

 the wild Bee in its cell, the Beetle in its wooden 

 chamber hollowed out within the trunk of the forest 

 tree. 



Others, again, display a still more remarkable instinct, 

 the perfect insect actually entering the water in order to 

 deposit her eggs within the bodies of aquatic larvae. 



N 2 



