IV INTBODUCTION. 



the simple eyes or ocelli (figs. 2 & 3, b), three in uumber; these 

 may be present or absent, complete, or distorted as in some of the 

 Sphegidcf. Below the vertex is the front (figs. 2 & 3, c), on which 

 are inserted the antenna' (fig. 1, d-f; figs. 2 & 3, e-f). The parts 

 ot the autenna are the scape (fig. 1, d; figs. 2 & 3, ?, e) and the 

 flngellum (fig. 1, e-f; figs. 2 & 3, /, /). The scape or basal joint of 

 the antenna is sometimes elongate as in the Heterogyna or Ants : 



Pig. 1. — Salins avreosericeus. Side view of head much enlarged.— «. Tertex ; 

 b, cheek ; c, compound eye ; it, scape of antenna ; e-f, flagellum of 

 antenna; q, elypeus ; h, mandible; J, maxillary palpus; k, labial palpus; 

 /, portion of maxilla. 



the Jlagellum is, as a rule, divided into eleven joints in the female 

 and twelve in the male ; the apical joint or joints in the latter sex 

 being sometimes more or less modified, e. g., curved into a hook as 

 in some of the Diploptera, spined aud excavate below as in some 

 of the Fossores (Bembex), or dilated and flattened as in a few of 

 the AntJiopliila. Below the base of the antennae is a more or less 

 conspicuous and shield-like plate called the clypeus (figs. 1,2, & 3, (/), 

 the form of which affords valuable specific or, sometimes, generic 

 characters. Beneath the elypeus and hinged on to its anterior 

 mar»in is the labrum (figs. 2 & 3, h) : this is variable in size 

 and form, and is frequently entirely concealed underneath the 

 elypeus, while in a few genera it is exserted aud elongate to an 

 extraordinary extent. The part underneath the labrum is the 

 epipharynx. The mandibJes (tig. 1, 7i: figs. 2 & 3, i, i) are hinged 

 to the apex of the cheeks below and fold over or under the 

 labrum ; under all modifications in size and shape they remain 

 conspicuously cutting or crushing machines. On the underside 

 of the lower or fate portion of the head is a hollow into which fit 

 the softer mouth-parts when at rest. These latter consist chiefly 

 of the labium and the maxillae (figs. 4 & 5). The labium is 

 attached to the side walls of the buccal holloAv, through narrow 

 joints, the lora and the cardines. The upper portion of the 

 labium forms the sulmeninm and mentum, ; from the apex of the 

 latter at the sides spring the labial ^alpi (fig. 4, A,-, A.-), and from 



