PARASITIC HYMEN OPTERA. 227 



ment in the perfect state. Agaihis and Aiysia, indeed, in 

 their types, present remarkable modifications of the lips and 

 jaws, but, after a few removes, these too subside into the 

 prevailing monotony. Of all the parts of the mouth, the 

 feelers seem to afford the most convenient means of methodical 

 division ; their differences, like most characters determined by 

 number, being easily seized by the eye and expressed with 

 certainty. Such a method comes recommended also by the 

 weight of authority, almost every recent arrangement of the 

 family resting principally on those organs. Analysis has 

 shown their variations to be of minor consequence in de- 

 termining relations between the subdivisions of Aphidius, 

 while the separation of that genus has made their application 

 to the rest more easy. The objections arising from the former 

 consideration will be lessened if we regard these last as nearer 

 in affinity to the genuine Ichneumones ; for they, throughout 

 their myriad species and multiplied gradations of form, adhere 

 almost invariably to one number, the incipient tendency to 

 change appearing only at one point. b And, indeed, in the 

 single genus we have been considering, their extremes of 

 variation are more distant than in all the remainder of the 

 Adsciti. The figure and proportion of the joints are more 

 constant in the maxillary feelers than in the labial, where the 

 diminution of the penultimate joint makes the precise number 

 sometimes difficult to determine, so that we shall gain in con- 

 venience by omitting the consideration of the latter at this 

 stage. Following, in other respects, the arrangement of 

 Von Essenbeck, let us place first those which have maxillary 

 palpi of five joints, composing the family named by him 

 Bracones. With respect to the nomenclature, it may be 

 remarked, that he at first applied the generic name of Bassus 

 to Cryptus manducator of Panzer, and from that type derived 

 the appellation of his second family ; more recently Bassus 

 has ranked among the genuine Ichneumones, being appro- 

 priated, by Gravenhorst, to a group represented by Anomalon 

 lastatorium of Panzer ; to this Von Essenbeck has conformed, 

 substituting the Latreillian genus Aiysia in its place, yet, 



b The genus Porizon, which betrays a departure from the type in other parti- 

 culars ; the predominant characters, however, are unchanged ; and the subgenus 

 Odontomerus may almost 'be described as a Porizon resuming in its mouth and 

 lower wings the ordinary character of genuine Ivhneumones. 



