COLEOPTERA. 205 



EXPLANATION OF THE PLATE. 



Fig. 1. Maxilla and maxillary palpus of Stenus juno (Fab.) % , taken near 

 Cambridge, Massachusetts. The terminal spine of the third palpal 

 joint is not represented, as it was entirely invisible in the original. 

 The triangular area to the left is the exposed surface seen when 

 in position to the left of the mentum ; the inner lobe is strongly 

 declivous just to the right of this triangle, in order to allow the 

 lobe to extend under the labium. 



Fig. 2. Maxilla and maxillary palpus of Areus annularis (Erichs.) 9« -At 

 the end of the outer lobe is to be seen a thin prolongation, along 

 the apex of which the setae are irregularly and arcuately bristling. 

 This prolongation, which forms the principal distinctive feature 

 in the maxilla of the present species and that of Stenus juno, is 

 of very peculiar formation, being an aggregation of parallel fibres 

 compactly agglutinated, and resembling almost exactly a piece of 

 fibrous gypsum, or of some varieties of asbestos. Among other 

 differences, may be noted the very much longer setae along the 

 outer edge of the outer lobe ; they are also much less numerous. 



Fig. 3. Labial palpus of Areus annularis 9 . In the position in which it is 

 figured, the spinous third joint is not seen, but the view is that 

 which best enables observation of the concavity in the second joint. 



Fig. 4. Labium of Stenus juno 9 , Cambridge, Massachusetts. The terminal 

 portions of the paraglossae are white, and of a granular gelatinous 

 texture, the ligula being yellowish-testaceous ; the line of de- 

 marcation between these portions is very distinct. The narrow 

 medial carina of the ligula is to be noted. The labial palpi are 

 attached to minute tuberculations at the anterior edge of the ligula. 



Fig. 5. Right mandible of Areus annularis 9 viewed internally. In this 

 position the full curvature of the mandible is not seen, as the 

 point of sight is nearly in the plane of the curve. 



Fig. 6. Mentum of Stenus juno 9 as viewed detached from the submentum ; 

 the narrow transverse area bordering it posteriorly is testaceous in 

 color, and serves to form the joint at the submentum ; it projects 

 from below the exposed surface. The narrow carinal ridge is 

 extremely strong, and the surface of the mentum is most strongly 

 impressed near the lateral apical angles. The carina terminates 

 anteriorly in a minute triangular extension of the anterior margin, 

 which is very slightly reflexed. The apical angles project as very 

 minute points in this species. 



