xlvi . INTRODUCTION. 



Sub-Order. ICHNEUMONIDEA/ 



All the members of this extensive group are believed to be parasitic 

 upon other insects, spiders, &c., excepting a part of the Cynipidae. It 

 consists of six ^ sufficiently distinct families, which are thus recognised : — 

 (i) Evaniidae alone have the abdomen rising from the dorsum of the nieta- 

 thorax ; (2) Cynipidae alone have the terehra partially coiled and rising 

 from near the base of the abdomen ; (3) Proctotrypidae alone have the 

 terebra tubular ; (4) Chalcididae alone usually possess geniculate an- 

 tennae, and the body of brilliantly metallic colours ; and, lastly, (5 and 6) 

 Braconidae and Ichneumonidae, of which the antennae are not geniculate, 

 and the terebra is divided into three pieces. These last two families 

 undoubtedly take precedence in the scale of Nature, on account of 

 the complexity of their specialised conformation and probably also of 

 their instinct, though little is known of the economy of the smaller 

 Ichneumonidea. 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, with the Braconidae, many genera exhibit a very intimate 

 affinity, and it becomes essential to remember that, — 



Ichneumonidae have two transverse nervures in the fore wing. 

 Braconidae have but one transverse nervure in the fore wing. 

 In a few genera of the former, however, e.g., Hemiteles and Orthocentrus, 

 the second transverse nervure, though always traceable, is often pellucid, 

 being usually stronger at its anal extremity ; and, in those genera whose 

 wings are rudimentary or wanting, no reliance must be placed upon such 

 neuration as may exist. In such cases, it is necessary to fall back upon 

 the tegument of the abdomen, which is flexible in Ichneumonids, e.g.., 

 Pezomachus, but hard and chitinous, with the central segments connate 

 and inflexible, in Braconids, e.g.., Chasmodon. 



Plence 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 

 geniculate ; the coloration not metallic, though often strongly nitidulous ; 

 and the second transverse nervure present, or, in apterous and brachyp- 

 terous forms, the venter not connate. 



A TABLE OF FAMILIES OF ICHNEUMONIDEA. 



(2). I. Abdomen emitted from dorsum of meta- 

 thorax Evaniidae. 



(i). 2. Abdomen emitted from apex of metathorax. 



(8). 3. Front wing with discoidal nervures. 



(7). 4. Terebra rising from near apex of the usually 

 depressed abdomen. 



(6). 5. Front wing with two recurrent nervures Ichneumonidae. 



(5). 6. Front wing with one recurrent nervure Braconidae. 



(4). 7. Terebra rising from near base of the usually 



compressed abdomen Cynipidae. 



1 I have striven throughout the work to follow the suffices proposed by the German Zoological 

 Society for sub-orders, families, tribes, &.c. 



'- The Chrysididae are considered to have possessed four cubital cells in the ancestral type, and 

 must, consequently, be grouped among the Vespoidea. 



