BRITISH ICHNEUMONS. 63 



Trihe 



CAMPOPLEGIDES. 



In temperate climates this Tribe is extremely abundant both in species 

 and individuals, extending from Lapland to the Mediterranean coasts, 

 but further south it seems to become decidedly scarcer and I know of 

 few or none below the equator; this may be due, to a certain extent, to 

 the superficial collecting that small Hymehoptera in general have at 

 present met with in tropical countries, where the larger and more con- 

 spicuous attract especial attention to themselves ; at least they go down 

 to the Tropic of Cancer, for I have described a good many from Bengal. 



With us, and throughout both the Palaearctic and Nearctic regions in 

 general, these insects are so numerous as to become perfectly bewilder- 

 ing, and so poorly are the species evolved in structure or constant in 

 colour that their differentiation is fraught with peculiar difliiculty. Even 

 the Tribal characters are best explained by negative features: The colour 

 is never testaceous, the external radial abscissa is not basally continuous 

 with the submarginal nervure as in the Paniscides, nor is the areolet 

 (though not infrequently wanting) ever obliquely quadrate as in the 

 ^lesochorides; the metathorax is not apically produced as in the Anoma- 

 lides, nor the second recurrent emitted from the cubital beyond the sub- 

 marginal as in the Ophionides; it bears no femoral tooth as in the Pris- 

 tomerides and the narrow stigma will distinguish it from the Ophionid 

 tribes already described. 



The possibility of reducing the vast mass of Palaearctic and large 

 number of British species to something approaching a natural classifica- 

 tion is owed, after Holmgren, to Prof. G. C. Thomson of Lund, who in 

 his great Opuscula Entomologia, fasc. xi, gives us a capital though all 

 too brief conspectus of them in 1887. Both Holmgren and Forster had 

 already devoted especial monographs to the larger and more conspicuous 

 species of Gravenhorst's compreliensive genus Campopkx, leaving the 

 smaller and more obscure kinds, with but few exceptions, massed in an 

 unwieldy genus, Livmaia, of which more than a hundred distinct species 

 were known in Britain alone in 1885. I have followed Thomson some- 

 what closely in the following account of these and have adopted his 

 genera throughout, for those sketched by Forster in 1868 were both 

 typeless and insufficiently diagnosed, often moreover established upon 

 the most trivial and inconstant characters {e.g. the presence or absence 

 of the metanotal costulae, which I find extremely variable in their 

 development, even in a single batch of individuals of the same brood 

 and I have, consequently, avoided its use whenever feasible). Recent 

 writers have been loo prone to adopt these ill-bred genera, and to place 

 far too much reliance upon the development of the external nervure of 

 the areolet. 



In the following Table of Genera especial care is necessary in regard 

 to the depth of the metathoracic concavity ; and the position of the 

 nervellus (as in the Orthocentrides, cf. Ichn. Brit. iv. p. 54, with which 

 the present groups also agree ) is now recognised as of beautifully 

 constant construction. 



