HYMENOPTERA, — ICHNEUMONID. 139 
the stigma is large, and the costal margin is thickened, or rather the 
costal and subcostal nerves are confluent, so as not to exhibit a sub- 
costal cell. The legs are long, and formed for running; the tro- 
chanters are biarticulate; the tarsi long and slender, the terminal 
joint being furnished between the ungues with a small obtuse un- 
guiculus. In Ophion the ungues are pectinated. The abdomen is 
generally long and cylindrical, or elongate ovate, and narrowed at the 
base into a short peduncle; on each side of which is a small tubercle, 
in which a minute spiracle exists. The ovipositor of the females is 
sometimes retracted, in which case the abdomen terminates in 4 
point. In the other species this instrument is exserted, and occa- 
sionally of great length, in which case the abdomen is more obtuse at 
its extremity. In the former species it is often difficult to distinguish 
the sexes when dried, except from some other character, as the 
annulus of the antenne, slenderness of the body, &c.; but in the 
latter, the males (De Geer, vol. ii. tab. 29. fig. 25. m.) as well as 
females (Ibid. fig. 23. m.) are furnished at the extremity of the 
terminal segment of the abdomen with the two inarticulated styles 
of which I have noticed the existence in the former families. Of the 
true construction of the ovipositor of the females I have hitherto met 
with no correct description. Réaumur (Mémoires, tom. vi. pl. 29.), De 
Geer (Mémoires, tom. ii. tab. 29.), Curtis (Brit. Ent. pl. 214.), 
Latreille (Gen. Crust, tom. iv. p. 2.), Gravenhorst (Jchneumolog. 
vol. i. p. 89.), and Burmeister (Manual Transl. p. 198.) have given 
figures and descriptions of this instrument and its details; but have 
failed in tracing its real structure. My figures 75. 8-13. will exhibit 
its structure as typically represented in one of the long-tailed species 
(Pimpla instigator), and which will be found to agree with that of 
Urocerus and Cynips. F%g. 75.8. represents a lateral view of the 
abdomen of the female of the last-named insect, exhibiting the eight 
dorsal arcs (numbered | to 8), the seven basal ones being spiraculi- 
ferous, the eighth furnished at the tip with the two minute styles 
(a). On the under side of the abdomen there only exist seven 
ventral arcs (numbered 1 to 7), from the last of which arises on each 
side a corneous elongated plate (4), which is the basal portion of the 
outer sheaths * (4,6) of the ovipositor; the apical part of these 
* Mr. Curtis, overlooking this basal portion, describes the sheath as arising from 
the superior angle, and as shorter than the ovipositor. Neither of which is correct, 
the basal portion of the sheaths and the eighth dorsal are of the abdomen being 
inaccurately represented in his figure as confluent. 
