468 
[March 
hidden by its two shells, the lower edges of the dorsal joints closing 
together so tightly as to appear united. In all four figures o is the 
ovipositor, ss the two sheaths of the ovipositor, v what is apparently 
the terminal ventral joint, and 5—1 the others. In Fig. I, a is an 
appendage to v which only exists in certain species, e. g. q. spongi- 
fica 0. S., q. inanis 0. S., and gallse tinctorim (Asia.) As the ovipo¬ 
sitor in certain specimens of several species often reposes in the piece 
projecting more or less from its tip, it is liable to be confounded with 
this appendage, but may always be distinguished by its not being hairy 
and by its non-presence there in other individuals of the same species. 
From the above comparison and from a careful examination of many 
dozen species in my Cabinet, besides those catalogued below as infest¬ 
ing the oaks of Illinois, and also from repeated dissections, I propose 
to separate the two families as follows:—* 
Cynipidae. Venter visible nearly throughout its entire length % more 
conspicuously so in 9 ? oi" if retracted within the abdomen leaving a gaping 
suture below. The joint which is appai;ently the last ventral, and which for 
convenience I call in 9 tli© ventral valve” ® (Fig. l,v) very long, and forming 
in 9 a sheath-like receptacle, convex below, concave above, which is occupied 
by the ovipositor, (Fig. I, o.) Sheaths (Fig. 1, ss) of the ovipositor, erected in 
repose, either vertically, or obliquely backwards and upwards, and strongly 
® The presence of this “ventral valve” in 9 is a very useful character to dis¬ 
tinguish the sexes in Cynipidoe, when, as often happens, the joints of the an¬ 
tennae are difficult to count, and the 3rd joint antennae is scarcely curved or 
excised below. Generally the “ ventral valve” is small, weak, thin and incon¬ 
spicuous; in the genus Synerges it is better developed; but in the genus Rho- 
dites 9 • ill Tribalia n. g. hatatorum 9 n- sp., and in Synerges rhoditiformis 9 
n. sp., it is abnormally enlarged and thickened, and forms a very conspicuous, 
thorn-like feature in the profile view of the abdomen. (See Harris Inj. Ins. 
Plate viii, figs. 6 & 7, Rhodites dichlocerus.) Baron Osten Sacken mentions this 
as a characteristic of the genus Rhodites, but has inadvertently omitted to say 
that it is peculiar to the 9 sex as he kindly informs me. {Proc. Ent. Soc. Phila. 
II, j). 44, and compare pp. 46 & 48.) In Rhodites 9 (which belongs to Cyiiipidee) 
there is ordinarily an angle of 45°—80° between the tip of the dorsum of the 
abdomen and the “ ventral valve”; but occasionally these two parts close to¬ 
gether, the acutely pointed “ ventral valve” projecting beyond the tip of the 
abdomen. In Figitidae these same parts are incapable of divaricating at an 
angle of more than 5° or 6°, and usually are closely appressed to each other as 
in Fig. Ill, and one does not project beyond the other because the two united 
form a boring apparatus,' whereas in Rhodites it is the “ventral valve” alone 
that forms the boring apparatus. 
