Exyston | BRITISH ICHNEUMONS. 193 

stigma broad, nervellus elongately antefurcal; calcaria mutic, claws 
simple. Length, 5—6o$ mm. 
At once known from £. cznc/ulum by the much shorter basal segment. 
This is the species recorded as British by Bridgman (Trans. Ent. Soc. 
1884, p. 432) under the name Céeniscus /riangulatorius, Grav. ; but, since 
he refers to Gravenhorst’s variety only and undoubtedly named the insect 
captured by Bignell, in the vicinity of Plymouth, from Holmgren’s mono- 
graph, it must be known under the above name. Gravenhorst says it 
occurs in May, but the specimen taken by Bignell at Horrabridge, was 
found at the end of June; Atmore subsequently took several at Kings 
Lynn in Norfolk; and I possess four captured by Beaumont at Plumstead, 
late in May, 1897, by Stanley Edwards at Lynton in Devon in 1890, by 
Col. Yerbury at Golspie in Scotland on 15th August, 1900, and myself 
took a male in the New Forest on 13th August, 1901, in Denny Wood. 
It was not uncommon on birch trees in Tuddenham Fen on 6th June, 
1910; Champion took a female at Aviemore in 1876, and Piffard found a 
remarkable little male of only 4 mm. late in June, 1900, at Felden in 
Hertfordshire. It is abundant at Wimbledon in June. 
3. subnitidum, Grav. 
Tryphon subnitidus, Gr. 1. E. ii. 144; Ste. Ill. M. vii. 234, ¢. Exyston sub- 
nitidus, Piank. Zeits. Hym. Dip. 1906, p.90, ¢. 
Mouth flavous with mandibles at base and apex, and part of clypeus, 
black. Antennae filiform, pale fulvous beneath, with the three basal 
joints entirely black. Abdomen black, with basal segment immaculate 
and sulcate ; remainder apically flavescent, with the fourth to sixth also 
laterally badious. Legs black with the anterior femora dull stramineous 
below, and their tibiae and tarsi paler. Wings subhyaline ; the broad 
stigma and tegulae black, radix stramineous; areola irregular and sub- 
petiolate ; nervellus antefurcal and intercepted below its centre. Length, 
5 mm. 
Marshall placed this Z7vphon in Creniscus, doubtless, on the strength of 
its author’s comparison with LZ. cénc/ulum ; it has since been lost sight 
of, till Pfankuch recently found the type to belong to this genus on 
account of its equal teeth, and the capital and petiolar structure. It is 
allied to Z.. brevzpetiolatum in its short basal segment; but is unknown to 
me, excepting ina somewhat poor though apparently correctly-named 
example from Desvignes’ collection in Mus. Brit. 
Gravenhorst knew but a single male, taken by Sturm near Nurnberg. 
We have nothing but the above specimen, and Stephens’ record to place 
it in our fauna: “ Found at the Hermitage in August, and in other places 
within the metropolitan district ; apparently not common.” 
ACROTOMUS, Holmgren. 
Holmgr. Sv. Ak. Handl. 1855, p. 222. 
Head somewhat tumidulous and shortly pubescent ; clypeus more or 
less convex, not deeply discreted and generally truncate ; mandibular 
teeth stout with the lower distinctly the longer. Thorax stout and ob- 
soletely pubescent; metathorax short with entire areae. Abdomen 
oblong-fusiform with the first segment narrow but not basally dilated. 
Legs normal with no hind calcaria. Areolet usually entire. N 
