EXTEENAL STRUCTITEE. 9 



pression terminating on either side in a fovea. The apical margin 

 of the clypeus is usually truncate, or sub-bisinuate, though 

 occasionally dentately reflexed or simply rounded. The cheeks, 

 which lie between the apical extremity of the eyes and the base of 

 the mandibles, and the temples behind the eyes, are more or less 

 broadly buccate, and the former vary in their length according as 

 the eyes approach or recede from the mandibles, which are 

 broader basally than apically, and sometimes basally as broad as 

 the cheeks are long. The apex of the mandibles, which lie folded 

 upon each other across the apex of the clypeus, is usually biden- 

 tate, the upper being in most cases much longer than the lower 

 tooth, but in some instances the teeth are of equal length or the 

 lower is wanting. Between the apex of the clypeus and the 

 mandibles the labrum is more or less visible, being round and 

 ciliated. The two pairs of palpi, the maxillary and the labial, are 

 elongate ; the former consists of five usually cylindrical, the latter 

 of two triangular and two cylindrical, joints. The mentum, 

 ligula, hypo-pharynx, etc., are not alluded to in descriptions. 



Fig. 1. Head of an Ichneumon. 



1, vertex; 2, ocelli; 3, frons ; 4, antennal scrobes; 5, point of insertion of 

 antennae ; 6, face ; 7, clypeus ; 8, cheeks ; 9, labrum ; 10, mandibles ; 

 11, ligula ; 12, maxillary palpus ; 13, labial palpus ; 14, eyes ; 15, orbits. 



The antennce are inserted between the eyes in the front of the 

 head. They are multi-articulate, as many as seventy joints being 

 found in such genera as Opliion. while in others the number 

 diminishes to fourteen, as in Stilpnus. The scape consists of the 

 t\vo basal joints (the radicula or minute basal not being 

 counted). The first of these is oval or shortly cylindrical, 

 with an incision on its outer side, in which is inserted the second 

 joint or pedicellus, having its apex always free, but shorter than 

 the basal joint. !Next follows a minute joint, termed the annellus, 

 which with the remainder of the antenna constitutes the 

 flagelluin. During life the antennae are porrect and held while in 

 repose straight forward, not recurved beside the body as in most 

 orders of insects. After death they very often become convoluted 

 and spirally coiled, as described by the older authors. 



