INTRODUCTION. 15 



Oil the reiitral aspect only five segments are normally visible, 

 the two basal ones iiaving permanently disappeared. Lacordaire 

 (Gen. Col. vi, p. 12) mentions two genera — Ithyccnis (North 

 America) and DicJiotracJielus (Europe) — in which there is a sixtli 

 segment. Leconte and Horn state that the number is never 

 more than five, the appearance of a sixth segment being merely 

 due to the accessory tergite of the male having been pushed into 

 a ventral position. While their interpretation may possibly be 

 correct in certain cases, the general statement that there is 

 never a true sixtli ventral segment cannot be maintained. In 

 those genera, such as Neocimhus and Pohjdels, in which the 

 females have a well-exserted eighth tergite, there is, paired with 

 tliis tergite, a strongly chitinised sixth ventral plate, which, 

 though normally concealed, is capable of being exserted. Its 

 occurrence in this sex has also been noted elsewhere and will 

 probably prove to be general. 



In the great majority of genera the first two visible segments 

 (in descriptions the two vanished ones are not counted) are more 

 or less soldered together, even though they may appear to be 

 separated by a superficial suture, the nature of this suture and 

 the relative lengths of the intermediate segments affording good 

 generic distinctions. The basal segments are entirely free in 

 only a few subfamilies, such as IIhixomacerin^, Ehynchitin.e, 

 Belin.t; and Eurbhynchin.e, 



Superficial clothing.— As compared with other Coleoptera, the 

 weevils are remarkable for the very large percentage of forms 

 that are clothed with scales. In a few subfamilies all the species 

 ure devoid of scales, but these are all groups containing very 

 few genera, such as Attelabin.e, EHYNcniTiNyE, Apionin.^, 

 Ci-LADiNiE, Belin^, TrypetintE, etc. In the Cossonin.e and 

 Calandrin.4; the occurrence of scaling is a rare exception, many 

 species in the latter subfamily exhibiting a characteristic pruinose 

 covering ; while in the Baridix^, A\-hich comprises a very large 

 number of species, the great majority are glabrous. Compara- 

 tively little attention has been paid by systematists to the structure 

 of the scales, though these often exhibit good specific, and even 

 generic, characters. They vary greatly in shape, and are some- 

 times fringed with hairs, while in some groups (e. g. Cleonin.i;) 

 each scale may be split up into a mere bunch of feathery filaments. 



In the squamose groups the intervals of the elytra almost 

 invariably bear more or less regular rows of setae, which frequently 

 furnish excellent specific characters. In certain pubescent genera, 

 such as Lixus and Larinus, the colouring is produced by a coating 

 of a fine powdery substance, which is very easily abraded. 

 Laboulbene insisted that this efflorescence was of a crypto<>-amic 

 nature (Ann. Soc. Ent. France, 1848, p. 301 ; 1850, p. 17), but 

 there can now be but little doubt that it is actually secreted by 

 the insects themselves, and Lacordaire (Gen. Col. vi, p. 417) and 

 others have recorded that tlie substance can be renewed by the 

 living insects after it has been rubbed off; in se\eral cases it 

 forms a regular pattern. In a few Eastern genera (Alcides and 



