16 INTRODUCTION. 



Sub-Older ENTOMOPHAGA or ICHNEUMONOIDEA. 



The whole of this very extensive group is believed to be 



parasitic upou other insects, spiders, centipedes, etc., excepting 



only a part of the Cy>'IPID.1£. It consists of six sufHcieutly 

 distinct families, which are thus recognised : — 



(1) EvANiinJE alone have the abdomen rising- from the dorsum of the 



metathorax. 



(2) CyNiPiDiE alone have the terebra partly coiled and emitted from 



near the base of the abdomen. 



(3) PROCTOTRYPiDiK alone have the terebra tubular and emitted from the 



apex of the abdomen. 



(4) Chalcidid^ alone are strong-ly punctate and briUiantly metaUie in 



coloration. 

 ,^. _, ) ( lack the second recurrent 



(5) Bbaconid^ / ^^^^^^ j^^^.g complete ) nervure. 



,,, -r l neuration *) have the second recurrent 



(6) IcHNEUMONiD.^5 j ( uervure. 



These last two families are undoubtedly the most highly 

 specialised in the sub-order, both as regards their structure and 

 probably also their instincts, though but little is known of the 

 habits of the smaller of even the Palisarctic Ichneumonid.i:. To 

 the first four families the last bears no very close resemblance, 

 and from them it will at once be distinguished with a little 

 experience. But many genera of Ichneumons exhibit so close a 

 resemblance to the Braconid.^ that the division in general use, 

 though very convenient, hardly appears natural ; they are easily 

 confused and the only sure method of discriminatiou is to bear in 

 mind that the Ich:n'eumoxid.e have a transverse nervure across 

 the front wing running down from the areolet to the anal uervure, 

 all trace of which is lacking in the Braconid.e. In a few genera 

 of the foimier, however, e. g., Ilemiteles, Orihocentrus, and Uomo- 

 cidus, this second recurrent nervure, though always traceable, is 

 often pellucid, though usually stronger at the anal extremity ; and 

 in those genei'a whose wings are rudimentary no reliance cau be 

 placed upon such nervures as may exist. In such cases as the 

 latter, and also in the wingless forms, it is necessary to fall back 

 upon the tegument of the abdomen, which is flexible beneath in 

 Iclmeumonids, e. g., Pezomachus and its brachypterous allies, but 

 hard and chitinous, with the central segments connate and in- 

 flexible, in Braconids, e. g., Chasmodon, Pambolus, etc. 



Hence we find that an Ichneumonid always has the abdomen 

 rising from the apex of the metathorax ; the terebra straight, not 

 tubular, exserted from the ventral surface near the apex of the 

 abdomen ; the antennae not genicidate ; the colour not or but 

 very rarely metallic, though often strongly shining ; and the 

 second recurrent nervure always present, or, in apterous and 

 micropterous forms, the ventral segments not connate. 



