Homocidus | BRITISH ICHNEUMONS. 103 

thorax. Thorax black, somewhat shining and very finely punctate; a 
large subhamate humeral mark white, g also with large pronotal mark, 
mesosternum apically and pleural lines, concolorous; mesosternum 
densely and very finely punctate, with speculum not smooth ; metathorax 
finely punctate, apically subrugose with areae wanting and lateral costae 
subobsolete. Scutellum apically and lateraily lined with white, rarely 
immaculate in g. Abdomen black and half as long again as thorax, 
apically smooth and hardly compressed; first segment short, basally 
excavate and coarsely punctate, with no carinae, postpetiole transverse, 
spiracles not prominent; second subtransverse, sparsely punctate, and 
between the transversely oval thyridii, densely striolate; third in ¢@ with 
a more or less conspicuous pale fascia. Legs somewhat stout and red, 
with the anterior basally paler in ¢ and sometimes black-marked in 9; 
hind tarsi and tibiae black, the latter sparsely setiferous externally and 
white nearly to their centre internally in 9, or mainly testaceous in g 
which also often has an infuscate band before, though never at, the base. 
Wings hyaline, stigma infuscate and not broad, basally pale; areolet 
irregular and subsessile; nervellus oblique, intercepted far below its 
centre. Length, 5—6} mm. 
This species may be regarded as the type of a small group of closely 
allied insects, having in common the scutellum not entirely pale and of 
normal convexity, areolet distinct, abdomen with no broad rufescent mark- 
ings, mainly whitish hind tibiae, and no or very obsolete petiolar carinae. 
The present is distinguished by the pale humeral marks, basally pale hind 
tibiae and its clypeal structure. 
This is a widely distributed insect on the Continent, where Schrank first 
captured it about Ingolstadt in May, and is very abundant in Britain. 
Desvignes’ @, which I have seen in the National Collection, is synony- 
mous; but his 9, which is not there, would appear to belong to Thom- 
son’s var. b, with only basal pale scutellar dots. Common in Norfolk 
(Bridgman); found commonly in Ireland (Haliday MS. in Dublin 
Museum); Devonport and Laira, Devon (Bignell); Harrogate in 1867 
(Roebuck); Bury St. Edmunds (Tuck); Felden in Herts (Piffard) ; 
Botusfleming in Cornwall, Nunton in Wilts, Bishops Teignton, Corn- 
worthy and Lastingham in Yorks (Marshall); Reigate (W. Saunders) and 
Shere (Capron), in Surrey; Guestling in Sussex (Bloomfield) ; Bonhill 
and Crookston in Scotland (Dalglish). In Suffolk it is very common at 
Foxhall, Tuddenham Fen, Ipswich, Monks’ Soham, Blakenham, Wen- 
ham, Henstead, Dodnash, Bentley, Eriswell, Southwold and Covehithe ; 
it is perhaps most frequently taken on the borders of woods, especially on 
the flowers of Heracleum sphondylium and in marshes on those of Angelica, 
and in September I have found it not rare on reeds in salt-marshes by the 
coast, nor is it uncommon in the gardens of large towns. Elsewhere | 
have observed it at Peterborough, Ryde in Isle of Wight, Matley Bog and 
Lyndhurst in the new Forest. My captures range from 27th May to 27th 
September, and its frequency does not appear to diminish during mid- 
summer, as is the case of most Aassides. We know nothing of its 
economy, though that it preys upon Syrphid larvae is rendered probable 
by my capture of a female on 28th June, 1903, investigating the green 
and unopened buds of Heracleum, covered with Aphis hieracii, Kalt. 
