Dr. David Sharp's Studies in Wiynchophord. 211 



idea : the membranous part thai connects with the body 

 is not exserted naturally; thus the symmetry is never 

 so complete as they lead one to suppose, and it is also 

 greatly interfered with by the muscles, as well as by con- 

 strictions, folds and pleats, and the alternations of very 

 hard parts with delicate membranes. In some forms 

 (such as C ion us) the tube can, however, be extended into 

 a form comparatively more elongate than in fig. 2. 



In these diagrams the hard (chitinised) parts are repre- 

 sented by thick lines, the thin lines being membrane. 

 The features shown by these diagrams are constantly 

 present in all Rhynchophora, except that the spiculum is 

 absent in one division of the Calandridae and in Platy- 

 pidae; and that in the group last named there are no true 

 median struts, the basal prolongations of the median lobe 

 being there projections with membrane between them. 



The Abdomen. 



The genitalia in Coleoptera are withdrawn into the 

 abdomen and completely concealed. Although the abdo- 

 men is not morphologically a part of the genitalia, yet the 

 two are so intimately connected functionally that neither 

 can be comprehended fully without a knowledge of the 

 other. There are, indeed, some who consider that the 

 genitalia in whole or in great part are really modified parts 

 of the abdomen, and Verhoeff entitles his paper on the 

 genitalia of Scolytidae, a study of the comparative anatomy 

 of the abdomen. 



In Rhynchophora the abdomen is greatly modified at the 

 base of the ventral aspect in coadaptation with the meta- 

 sternum and hind coxae. On inspection five ventral 

 plates are seen, and these in descriptions are called the 

 first (basal) and so on to the fifth. There is membrane 

 concealed at the point of junction with the sternum, and 

 also a hard more or less perpendicular part or phragma. 

 These parts (which are not visible except by taking off the 

 abdomen) are considered to represent the sternites of two 

 segments. This is rendered in the highest degree probable 

 by the fact that the corresponding dorsal portion of the 

 abdomen lias seven plates in place of the five ventral ones. 



In addition t<> the seven easily recognised segments 

 there is an eighth one. the dorsal part of which is usually 

 large, while its ventral plate is small; the ventral plate 



