CURCULIONIU.E. 



always slightly raised above the adjoining surface oi: the mandible, 

 but in many Tanymecides it is markedly prominent and can be 

 readily seen when the end of the rostruui is viewed from above 

 (fig. 4, b). This structure, which is known as the mandibular 

 scar, serves as a support for a temporary false mandible (fig. 5), 

 or mandibular appendage, which in the vast majority of species 

 normally breaks off soon after the emergence of the adult, though 

 persisting in a few exceptional individuals ; there are, however, 

 a few genera in which it appears to be retained permanently, 

 namely, in both sexes of the Pahiearctic Psalidium, and in the 

 males only of the Australian Pro^tomus, while the same is also 

 possibly true of a new Indian genus, NothognatJms (fig. 77). 



The false mandibles vary considerably in their form, but they 

 are of no value for purposes of classification, often differing 

 markedly in closely allied species ; they are usually less de- 

 veloped and more readily deciduous in the females, and are a 

 conspicuous feature of the rostrum in the pupal stage. 



Fig. 5. — Mandibular appendages of: a, Episomus Jigtiratiis, Karscb ; 

 b, Mylloccrus discolor, Boh. ; c, Aati/cus lateralis, F. 



It is generally assumed that the newly emerged insect utilises 

 these organs for breaking its way out of the cocoon or through 

 the soil beneath which it has pupated ; and this conclusion finds 

 support in the fact that the appendages are present only in those 

 species that have obtuse mandibles, the edges of which are deep 

 vertically and meet like a pair of pincers, being more suitable 

 for crushing than for cutting. M. P. Lesne has recorded an 

 observation in this connection made by himself on newly emerged 

 examples of a European species, Exomias pellucidus, Boh. (Bull. 

 Soc. Ent. Erance, 1899, p. 143): — "Propped up in its sub- 

 terranean chamber, the weevil opens its mandibles and seizes a 

 particle of earth between the long appendages ; it then inclines 

 its head beneath its thorax and deposits the particle between its 

 legs," this operation being continued so that it gradually works 

 its way up to the surface. 



In the majority of the PHAyEEOGNATiii the mandibles are strongly 



