Exochus | BRITISH ICHNEUMONS. 31 

I have carefully traced Thomson’s distinctions between his 77zclis/us 
and Zxvochus, with the result that I cannot consider them distinct, since 
the following are the only characters he enumerates :— 
TRICLISTUS, Thoms. EXOCHUS, Thoms. 
Ocelli forming a triangle. Ocelli forming nearly a curved 
line. 
Frons very shortly cristulate. Frons with no cristula. 
Scape not arcuate. Scape arcuate. 
Intermediate calcaria of equal Intermediate calcaria strongly 
length. unequal. 
[ Genal sulcus wanting ; Genal sulcus often impressed ; 
Head always black; Vertex often pale-marked; 
Areolet often present ; Areolet always wanting. | 
The last three characters are inconstant and cannot add to the stability of 
the former genus. As to the Foérsteran names, the presence or absence 
of alar areolet is a capital feature on paper, but in the present group one 
often finds a well marked areolet in one wing and but the faintest 
indication thereof in the other of the same specimen; and I am of 
opinion that much future synonymy has been erected upon this variable 
feature. Bridgman regarded it as ‘‘a question if such trivial distinctions 
as the absence of areae on the metathorax have any right to be raised 
into species” (Entom. 1880, p. 258): how much less then should we found 
genera upon the lack of a small transverse carina, be it ever so constant ; 
and, in fact, it is, in this group at least, a capital character for dividing up 
the species into groups, though not equally apparent in both sexes. 
Polyclistus, Pertope, Chorinaeus, etc., have well marked characters and dis- 
tinct facies, in spite of what Vollenhoven says of them, but I think it 
invidious to them to raise the obscure features of Z7ic/isfus and Amesolytus 
to equal rank. Moreover, species occur with both areolet and costulae, 
for which even FoOrster was not prepared with a generic name, for the 
head in these is often normal and unlike that of A/e/acoelus. In the fol- 
lowing account of our species of Lxvochus I have somewhat closely 
followed Prof. Thomson, who, though apparently obscure on many points 
of primal distinction will be found to have given very beautiful differential 
characters if his remarks be worked in conjunction with the more detailed 
descriptions of authors. Seventeen species were enumerated as British 
by Marshall in 1872, and I added eleven in 1901; to these twenty-eight, 
four new to Britain and one to Science are here enumerated with the 
result that, after synonymizing several, the total stands at thirty out of the 
sixty-five known palaearctic kinds.* 
* Besides those enumerated, I possess two malesand a female of a species I am unable to tabulate, 
evidently belonging to Thomson’s unsatisfactory intermediate section with the areolet wanting and 
the hind calcaria shorter than the hind tibial breadth though by no means minute (c/. 34 ef 43 in the 
Table). They are black with the femora and tibiae entirely red, the facial fascia and vertical dots 
palein ¢ but immaculate black in ¢. The species appears most closely allied to E. tardigradus, 
Gr. (nec. Holmgr.), from which the tibial colour precludes it. In every respect it is intermediate 
between E. prosopius and E. parvispina. It is probably a common kind, since I have it from Nantua 
in France (ex coll. Marshall), Shere in Surrey (ex coll. Capron) and took the type at Lyndhurst in 
the New Forest on 17th August, 1901. No published description, however, quite tallies with it, so I 
tentatively propose to term it Exochus intermedius, Morl, 
