Exelasics.] BRITISH ICHNEUMONS. 295 



Observations upon the copulation of Ichneumonidaeare extremely rare ; 

 Gravenhorst collected a hundred thousand of them without meeting with 

 a single example of it, but I have once met with it in the present species, 

 of which both sexes were bred out on the 5th of June, 1900. In this case 

 the pair remained quiet quiescent for half an hour ; the J held the 9 

 with his anterior legs, the hind pair being retracted and in no way in 

 use ; the J antennae were porrected, but those of the 9 were laid back 

 along the sides of the thorax. 



I have no hesitation in asserting that this is the commonest species of 

 all the Ichneumonidac in Britain, though its economy was for long un- 

 known. Curtis, writing in i860, says "It is difficult to account for the 

 absence of the surface-caterpillars from our field crops for many years 

 together, unless, as is generally the case, they are occasionally over- 

 powered by parasitic insects ; it is therefore not a little remarkable that I 

 have never met with any of the parasites which we may presume are 

 attached to these caterpillars ; it is true that, as far as regards the Xoctiia 

 brassicae, I find in gardens in June and July great numbers of an ichneu- 

 mon, called Exiiastes oscitlatoiiiis of Fabricius, which appears to accom- 

 pany that species, but, never having bred it, I have no direct evidence of 

 their being connected in their economy" (Farm Insects, 130). Mr. 

 Wigin has, however, confirmed the abo\-e connection by breeding nearly 

 a thousand of this parasite from JMaiiustni brassicae and Hadcna ohracea at 

 IMethlcy near Leeds ; Wattam at Huddersfield and Brischke in Prussia 

 have also bred it from the former host ; and Clutten at Barnsley from 

 both of them. It is also said to have been bred from Retinia pinicolana 

 (Proc. S. Lond. Soc. 1890) and Miami funincula (Entom. 1881, p. i + i). 

 I have seen it, or it is recorded, from Land's End, York, Earlham near 

 Norwich, Essex, Barnstaple, Lidford, Nottingham, Carlisle, Aberlady, 



through a single tiny hole in or near the extremity of the cocoon. {5) In one cocoon the Chalcid 

 larvae, though still moist, appeared to have died of some disease akin to constipation, since part of 

 their bodies is quite hard in a circular lump, while the rest is soft and fleshy. (6) Chalcids rarely 

 consume the whole Ichneumon, though I found them to have done so in one or two cases ; they appear 

 to emerge from their host's abdomen when the latter is about half formed, since the abdomen is found 

 to be much erosed and shrivelled. (7) In one case the Mesocliorus larva had emerged from the 

 Exetastes larva, probably upon finding the latter moribund, and both were separately dead. (4a) In 

 one instance only the Chalcid's hole of emergence was in the centre of the cocoon, near the girdle, 

 in which case the whole of the larva almost had been consumed, and interiorly the hole was jagged 

 and somewhat quadrangular, though externally circular and a little larger than is usually the case — 

 ? distinct species of Chalcid. 



Wigin sent (31 x 00) another 100 cocoons, from which 10 (? <? and 6 ? ? emerged, 12 i i and 1 ? 

 had cut holes but failed to emerge, and 7 cT cT and 2 ? ? Mesocliorus had emerged with no failures, 

 between 7th and 25th of the following June. Thence to the 30th June, 7 ii and 6 ? ? Exclastes 

 and 9 Mesocliorus emerged. Subsequently 10 cT cT and 3 ? ? Exetastes and 20 Mesocliorus emerged. 

 In one case I watched the J emerge : the cocoon is saturated with oral fluid (? from the ligula) and 

 the mandibles bite it away, as a moth caterpillar eats the edge of a leaf, in sweeping semicircles 

 (unlike the Cimbiciiiae, etc.), when the hole is large enough the insect walks straight out, head first, 

 with no hesitation. Of the remaining cocoons I noted :— (8) Three larvae died of mould, four from 

 injuries or draught, and three more were dead though still soft and black ; two nujiae died ol injuries 

 or dryness, (g) One Mesocliorus died, though fully formed, through the cocoon being impressed and 

 another nearly fully formed from the same cause, which was not apparent in a third, dead in the 

 same state of development. (10) One contained 18 live yellow Chalcid larvae and pupae — on 

 5th April, 1902 — together with a dead pupa, certainly of Mesocliorus mandibularis. 



In October, 1901, I received two more large consignments from the same source, which went to 

 show that the date of emergence sometimes extends to the end ol July, that the larva does not 

 undergo its ccdysis till the following April (as is usual in all Hymenoptera), and that these Exetastes 

 — perhaps most I(^neumonidae — seem to almost invariably emerge between midnight and 9 a.m. the 

 following mornine. 



