286 BRITISH ICHNEUMONS. [ Monoblastus 

This species is probably no more than a colour variety of M/. exstir- 
patorius, from which its author says it differs only in its immaculate black 
scutellum and darker front coxae. The legs, however, are very variable 
and Holmgren gives four forms showing the hind femora may be more or 
less broadly infuscate or, with their tibiae, entirely rufescent, as also may 
be their tarsi, and the anterior femora are sometimes basally black, com- 
bined with the third segment almost entirely testaceous. Closely allied 
structurally to Evromenus brunnicans and superficially similar in colour, 
but with face pale and clypeus not discreted. 
“The JZ. palustris larva was cylindrical, the head and first segment and 
the two apical segments quite white, the intervening space being green 
from the interior parts of the creature showing through the skin. There 
was a very dark green line, bordered by white granules along the dorsal 
area, throughout the length of the green part, lateral lines, ventro-lateral 
lines showing only in the segmental divisions, and a dark ventral line. I 
counted fourteen segments, including the cephalic one. There was a 
very slightly discreted border, not very evident. The mouth parts were 
discreted with fuscous and the antennal tubercles large, concolorous, and 
not protruding beyond the level of the head.” 
It is said to be not infrequent in marshy places in Sweden and southern 
Lapland; and Brischke has bred it in Prussia from the sawflies, Mema/us 
cirrhopus, NN. gracilis, Selandria hyalina (Blennocampa assimilis) and— 
Dalla Torre ascribes to him—Dzneura verna. It occurs in France and was 
introduced as British by Marshall in 1872 on the strength of a single 
specimen in his collection from Bugbrooke in Northampton; there is 
another there from Nunton, in the British Museum, with the two females 
referred to by Stephens, as having been “ found in June, near London.” 
All these I have examined; together with those concerning the economy 
of which Mr. Stenton has given so admirable an account and figure 
(Entom. 1911, p. 87) :—A female was observed on roth June, rgro, to 
oviposit in a larva of Emphytus cinctus at Herne Hill near London and, 
on being confined in a box, was supplied with further larvae of the same 
species of sawfly, upon which it almost instantly laid eggs close behind 
the head; the oviposition occupied but a few seconds and the host in 
this case made no resistance, though the usual practice is to violently 
throw themselves from side to side when attacked, sometimes falling to 
the ground with the parasite attached to their bodies ; at least four host- 
larvae were parasitised by each ichneumon daily. From the sawfly larva 
attacked on 1oth June that of the parasite emerged on 27th July follow- 
ing, leaving nothing but the shrivelled skin. The larva then spun silken 
strands (probably part of an artificially aborted cocoon) and on rst 
August signs of pupation were manifest, completed on znd; the pupa 
gradually deepened in colouration from 19th to 25th August, on which 
morning an active male was emerged. In all five females were captured 
in the same locality, where it was conjectured to be not uncommon in 
gardens by Mr. Stenton, whose description of the larva I have given above 
2m extenso, as probably typical of ichneumonidous Tenthredinid parasites 
in general. 
