BRITISH ICHNEUMONS 27 



Tribe 



PORIZONIDES. 



This Tribe is one of the most natural and easil)- recognised groups 

 among the whole Ichneumonidae. It is primarily characterised by the 

 short and extremely broad radial cell, formed by the subrectangular 

 geniculation of the radial nervure at its junction with the inner nervure 

 of the always externally incomplete areolet. In the present Tribe this 

 inner nervure is termed the areolar and, unlike nearly all other Tribes, is 

 continuous with or emitted by the cubital nervure but slightly before the 

 second recurrent nervure. The lack of external nervure of the areolet 

 resembles the same feature in the Cryptid genus Hemiteles; and we often 

 find so great an analogy with that genus that it is only by the rectangular 

 radius and the apically compressed abdomen that the present group is to 

 be differentiated. One of the main difficulties of the Ichneumonidae is 

 obvious relationship between groups, which are in other respects far 

 removed. That the present is truly Ophionidous is, however, undoubted ; 

 the abdomen is invariably compressed, unlike Hemiteles much more 

 strongly in the males than the females, the petiole is always distinct, 

 usually extremely slender and often elongate, the metanotal areae are 

 always incomplete with at least the costulae wanting, and what is referred 

 to in descriptions as the basal area is, in reality, the areola, for the 

 petiolar area here rises so far towards the metathoracic base as to occupy 

 more than half that segment. Upon this point I should like to express 

 my scepticism in the value of the unicarinate basal area, upon which 

 species and even subgenera have been founded; in this group the 

 presence or absence of this area is extremely variable — it may be entire, 

 longitudinally multicarinate, longitudinally unicarinate or wanting in the 

 same species, as I have shown in Diaparsus geminus. 



Respecting the hosts of this group, they would appear from such 

 scattered evidence as has hitherto been adduced to have to be sought 

 among the Coleoptera, usually among those Coleoptera which subsist 

 upon fungi; and the latter circumstance renders one suspicious. Besides 

 beetles certain Tineae moths and a great many Mycetophilid diptera 

 feed in fungi, and I am not aware that these parasites have been subjected 

 to a more rigorous investigation than their emergence along with the 

 beetles affords; they may even, like the INIesochorides, be hyperparasitic, 

 though such does not seem probable. I think Dr. Giraud must have been 

 mistaken in supposing he had bred a species from Chrysopa perla, one of 

 the neuropterous Lace-wing Flies. 



A great many more species is known in the neighbouring countries of 

 Europe than has yet been recorded from Britain ; but I have, among my 

 three hundred specimens of this Tribe, found it necessary to add but one 

 to those compiled by Desvignes, Marshall and Bridgman. Considerable 

 care is necessary to the correct elucidation of these often very small 

 insects, though no great difficulty will be found attached to the task, if 

 long series be available, and only five of my specimens baffled me; but 

 in the case of isolated individuals, and especially males, it is a very 

 different matter. 



