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OBDEB HYMENOPTERA. 

 Family ICHNEUMONID^E. 



About half the known Indiau forms of this important family 

 are dealt with in the following pages. These insects were well 

 known superficially long before the time of Linnaeus, on account 

 of their wonderful habits and instincts ; still even yet the family 

 has received but little attention, because the extreme specific 

 similarity, in conjunction with much individual variation, often 

 Tenders the discrimination of the species a matter of considerable 

 difficulty. Typical examples of the various subfamilies are most dis- 

 tinct and unmistakable, but the outlying genera such as Meyastylug, 

 Atractodes, and Exetastes are difficult to place correctly in natural 

 sequence ; and however distinct they may appear superficially, the 

 most widely separated and incongruous of ICHXEUMONID^E will be 

 found to differ comparatively little one from another in their 

 structure. 



De Geer was the first author to propose dividing the Terebrantia 

 or Entomophaga into sections depending on the sessility or other- 

 wise of the basal abdominal segment upon the raetathorax, which 

 method was elaborated by Schrank in 1802, and further supple- 

 mented with characters drawn from the neuration by Jurine in 

 his ' Nouvelle Methode de classer les Hyineuopteres ' of 1807. 

 In 1818, Gravenhorst and Nees von Esenbeck drew up the first 

 satisfactory system of natural sequence, which was followed by 

 the former's ' Ichneumonologia Europaea.' This work deals 

 exhaustively with the ICHNEUMOXID.S as understood to-day, to 

 the exclusion of all other Terebrant Hymenoptera, the characters 

 utilised for their subdivision being : a compressed or depressed 

 abdomen ; a petiolate or subsessile abdomen ; the shape of the 

 head ; presence or absence of the areolet ; extent of exsertion of 

 the terebra ; shape and convexity of thescutellum ; and many other 

 pertinent points ; upon these twelve genera and sixty subgenera 

 are based. The principal of the former were Ophion and Banchus, 

 which alone have the abdomen compressed ; Pimpla and Xorides, 

 with the abdomen subsessile and the terebra exserted ; Tryphon 

 and Bassiis, with the abdomen sessile, but the terebra concealed ; 

 Cryptus, with petiolated abdomen and the terebra exserted ; and 

 lastly, Ichneumon, with petiolated abdomen and concealed terebra. 

 These genera constitute the basis of modern classification ; and 

 although the sexes were at that time to a large extent considered 

 distinct species a common error, first indicated by Schrank, in 

 1781 it would be quite impossible to refer here to the subtle and 

 gradual modifications which have since been found from time to 

 time to be needful, or to mention the many hundreds of genera 



