INTBODUCTION, 



HISTORY. 



THE IcffifEUMONiDjE were first definitely separated from the 

 remainder of the parasitic Hymenoptera by Professor Graven- 

 horst in 1829, when he published his ' Ichneurnonologia Europsea,' 

 wherein he limited the family to those Parasitica having strong: 

 wing-nervures, of which 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 he 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- 

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

 to any appreciable extent dared to depart from the mode of classi- 

 fication therein laid down. 



The peculiar difficulty experienced by the student of these- 

 parasites is the extreme similarity in structure of specimens 

 which are obviously specifically distinct; and hence Graveuhorst 

 relied in a great measure on colour, always an unsatisfactory 

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

 as exist are so minute 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, who contributed a monograph on the 

 genus Ichneumon 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 'Ichneumonologia Suecica ' of 1864-89. Gravenhorst had 

 divided the family into five groups, and Holmgren elaborated the 

 OPHIONIN^E in 1858, the TRYPHOI^IN^E in 1859, and the PIMPLIIO;. 

 in 1860, on structural characters. 



Nothing had been done to elucidate the CRYPTIN^, 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 Pezomachus in 1850 ; and 

 some new species of the family were somewhat inadequately 

 described about the same time by Eatzeburg from the German 

 forests. 



