INTRODUCTION. 



History. 



The IcH^rauMOiN-iD.Ti; were first definitelj separated from the^ 

 remaiuder of the parasitic Hymeuoptera by Professor Graven- 

 liorst in 1829, when he pubHshed his ' Ichnemnonologia Europfea,'' 

 wherein he Hmited the family to those Parasitica havintr strono- 

 wing-uervures, of M'hich the second recurrent was very definitely 

 present. He not only described the whole of the European 

 species known to him in a collection of a hundred thousand 

 specimens, but lie also brought forward in a concise and easily 

 assimilated form all that his predecessors had done in the subject, 

 and gave detailed accounts of every published species unknown 

 to himself. This work laid the foundation of our present know- 

 lodge of this family, and it is comparatively recently that we have 

 to any ap])reciable extent dared to depart from the mode of classi- 

 fication therein laid down. 



The peculiar difficulty expei-ienced by the student of these 

 parasites is the extreme similarity in structure of specimens 

 which are obviously specifically distinct ; and hence Gravenhorst 

 relied in a great measure on colour, always an unsatisfactoiy 

 guide, for his specific distinctions; indeed, such structural points 

 as exist ai'e so minnte that their neglect by the earlier writers, 

 can readily be understood. As more and more workers bore their- 

 testimony, however, structure speedily took the place of colour in. 

 systematic works. The first subsequent author worthy of note- 

 was Prof. C. Wesmael, ^^"ho contributed a monograjih on the- 

 genus Iclineumon to the Brussels Academy in 1844 ; to this the- 

 same author added seven valuable supplements during the follow- 

 ing fifteen years, and in 1849 he published a revision of Jurine's: 

 genus Anomalon. Where Wesmael left the subject, it was taken. 

 up by Holmgren, who considerably advanced our knowledge in 

 his ' Ichneuraonologia Suecica' of 1864-89. Gravenhorst had' 

 divided the family into five groups, and Holmgren elaborated the 

 Opnro>-iN,E in 1858, the Tiitpiio>^i]S'.5; in 1859, and the Pimplin.i:. 

 in 1860, on structural characters. 



Nothing had been done to elucidate the Crtptin.b, however 

 before 1865, when Taschenberg redescribed Gravenhorst's types 

 in a somewhat perfunctory manner, excepting Dr. Arnold Forster's 

 too elaborate Monograph of the genus Pezomachm in 1850 ; and 

 some new species of the family were somewhat inadequately 

 described about the same time by Eatzeburg from the German 

 forests. 



B 



