INTEODUCTION. 



S uborder RHYNCHOPHORA . 



The Cueculionid.i:, or Weevils, belong to a very well-marked 

 division of the Coleoptera, which is generally treated as a sub- 

 order under the name of Ehynchopiiora, But although the 

 members of this assemblage can be readily recognised by their 

 general facies, no single structural feature has yet been dis- 

 covered which characterises all the species to the exclusion of 

 other Coleoptera. 



As lirst pointed out by J. X. Leconte (' American Xaturalist,' 

 1874, p. 385; Proc. American Phil. Soc. xv, 1876, p. 1), the 

 most representative characteristics of the suborder are the con- 

 solidation of the sclerites on the lower surface of the head 

 and on the prosternum ; of these the cephalic structure is the 

 more important. 



In normal Coleoptera tliere will be observed on the posterior 

 portion of the lower surface of the head two longitudinal sutures, 

 either straight or curved, and varying in their direction and 

 approximation. These are known as the gular sutures, and the 

 piece lying between them is the gula. In the Ehynchophora, 

 with a few exceptions, the gula has entirely disappeared and 

 there is only a single median suture, which itself is sometimes 

 evanescent or even absent (fig. 2). Leconte stated that this 

 coalescence of the gular sutures did not occur in any species 

 outside of the suborder, but this has been contested by H. J. 

 Kolbe (Arch. Naturg. 1901, Beihelt, p. 95), who says that in 

 certain genera of the Passaxdrin^ (Cucujid.i:) and TrogositiD-t: 

 the gular structure is similar to that in the Ehynohophora. I 

 have been luiable to confirm the latter statement, for in all the 

 genera which I have examined of the groups specified two gular 

 sutures are undoubtedly present. 



Per the present, therefore, we may accept the disappearance 

 of the gula as a character peculiar to the Rhynchophora. But 

 Dr. C. J. Gahan has pointed out that there are a few genera in 

 the group for which it does not hold good (' Entomologist,' xliv, 

 1911, p. 217) ; these are lihinoviacer and Oxycorijnus (CuRCU- 

 LioNiD^), and some ycOLYTin.E, such as Crossotarsus. AVith 



B 



