RHYNCHOPHORA. 175 



they vary in the number of their joints from eight to 

 twelve, and are inserted on the sides of the rostrum, in 

 two cavities or scrobes, which assume the form of pits or 

 furrows. These cavities often cause two side-pieces to 

 appear on the upper side of the apex of the rostrum, 

 called winglets, or pterygia, which are greatly developed 

 in Otiorhynchus and its allies. With one exception, the 

 parts of the mouth are, comparatively, of little assistance 

 in classifying these insects, the ligula and palpi (which 

 are small and short) exhibiting but little variation, and 

 the maxillae being usually single-lobed : the mentum, 

 however, affords a great diversity of structure, being 

 either abruptly truncate at its base, or provided with a 

 neck, and in either case received into a more or less deep 

 emargination of that part of the head that supports it. 

 This neck is wide, but of very little depth, in the species 

 with a short rostrum ; but in those that have a long 

 rostrum it is elongate, and, in proportion to its elonga- 

 tion, the mentum is reduced, so as to appear sometimes 

 entirely 'absent. The mentum, varying thus in develop- 

 ment, either wholly covers the maxillae (except sometimes 

 at their base), or leaves them free; and it is upon this 

 structure that Lacordaire has based his classification of 

 the section, which he primarily divides into the Adelo- 

 gnathes (in which the maxillae are entirely, or for the 

 greater part, hidden by the mentum), and Phanero- 

 gnathes (wherein they are completely uncovered). 



As, however, the older system of Schonherr is generally 

 used in this country, and (although more artificial) is 

 perhaps easier of comprehension by a beginner, and 

 sufficient for the mere arrangement of the British species, 

 it will (though sure to be eventually displaced by the 

 wider views of the gifted French author) be followed, for 

 the most part, in the present work. 



