N3. 



PREFACE. 



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The Ichneumonids contained in the present volume are without doubt 

 the easiest to identify of any occurring in Britain ; and the beginner in 

 this branch of the Insecta will consequently do well to study them first, 

 before going on to the more abstruse and difficult divisions of Ichneu- 

 monidae. The genera are, almost without exception, very definitely 

 defined and the species fall into tolerably natural sequence. This group 

 is further to be urged as the easiest introduction to our subject as a whole 

 on account of the abundance of the species comprised in it : of our two 

 hundred and eleven British species there are but forty that I do not possess 

 in my own collection, after no more than ten years collecting. The 

 Cn-ptinae are almost equally ubiquitous, but in its case the species are so 

 difficult to distinguish and in fact appear to so gradually and impercepti- 

 bly merge into each other that facility of determination is restricted to 

 but a comparatively few of the larger and more conspicuous kinds. 

 Moreover compared with the numerical superiority of the British represen- 

 tatives, they must yield to the present group ; for in the same length of time 

 I have only been enabled to amass 233 species. The very great similarity 

 between species and dissimilarity between the sexes of the same kind are 

 the principal drawbacks to the study of Ichneumonidae; often one finds 

 authors arbitrarily associating as sexes of the same, insects which have no 

 more right to be treated as specifically identical than that which is afford- 

 ed by the more or less analogous exoskeleton. Unfortunately this 

 method is unavoidable (and I am guilty of it myself) unless one is con- 

 tent to multiply the number of species by giving sexual names, as Forster 

 has so frequently, to insects whose relationship is not established. But, 

 as Shuckard very truly says (Foss. Hym. 159), " Nature is too Protean to 

 be bodiced " by any hard and fast lines or rules ; and in the case of the 

 Ichneumonidae copulation is so rarely witnessed — I have seen but two 

 instances — that this basis of a knowledge of sexual affinities is practically 

 denied us. 



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