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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



mentum does not extend as far as the origin of the palpi as in the 

 two other species mentioned above. 



The mentum (M) is a submembranous triangular plate the base 

 of which is anterior. The posterior angle is narrow and strongly 

 produced. Anteriorly it is fused with the palpiferal area of the labium. 

 A single bristle and a puncture (h) are situated on the antero-lateral 

 angles. The name proposed is seta menti. 



Tahi-E II. — Comparison of head setal arrangement. 



Seta 



Chaetoptcllus 

 vestitus 

 Fuchs. 



Dendroctonus 



valens 



Lee. 



Gnathotrichus 



materiarius 



Fitch. 



Fronto-lateralis .... 



Epistonialis 



Clypei 



Labralis 



Verto-mediana 



Verto-lateralis 



Geno-lateralis 



Geno-mediana 



Epicrano-lateralis . . 

 Mandibulae-dorsalis 

 Mandibulae-lateralis 

 Stipitis inaxillaris . . 

 Palpiferae maxillaris 

 Palpo-maxillaris . . . 

 Lacinio-maxillaris . . 

 Submento-iateralis. . 



Menti 



Labio-palpiferis . . . . 

 Ligulae-distalis . . . . 

 Ligulae-mediana . . . 

 Ligulac-basalis 



6 

 I 

 I 

 I 

 12 

 2 

 6 

 5 

 I 

 2 

 I 

 I 

 2 

 I 

 3 

 3 

 I 

 2 

 I 

 I 

 I 



The ligula (Li) consists of a circular plate largely surrounded by 

 the mentum. From subdivisional parts the base of the ligula is visible 

 from which it is well defined by faint sutures and the palpi (Pp). 

 The base bears a single pair of setae. They are present as two short 

 bristles and are called the setae ligulae l)asalis. The palpiferal area 

 is situated on both sides of the base. The part anterior to the base of 

 the ligula and between the palpi may be designated as the distad end 

 of the ligula. The palpi are two- jointed. The palpiferal area bears 

 two setae (j) which are called setae labio-palpiferis. The distal area 

 of the ligula is armed with two pairs of setae. Proposed names : setae 

 ligulae mediana and distalis. 



