Dr. David (Sharp's Studies in Rhynchophora. 219 



As the sac is the part of the coleopterous genital tube 

 that has been hitherto least investigated, I shall venture 

 to say a little more about it than my knowledge really 

 justifies; for its study is much more difficult than that of 

 any other part, so that it has been too often passed over 

 entirely, or without a word as to its being the essential organ 

 of intromission, to which the other parts of the mechanism 

 are merely accessory. The membranous part of the sac — 

 its walls and lobes— and any chitinous armature borne 

 thereon must be considered as conveyers of the transfer 

 apparatus to the spot where it can be effective. The 

 functional orifice appeals to be always minute even when 

 the other parts of the apparatus are voluminous. In the 

 case of the very long — whip-like — flagellum it is most 

 difficult to actually see the aperture, for the structure 

 cannot be set on end, but the long and slender apparatus 

 may be said to be as fine as it is possible for a chitinous 

 duci to be. Now, though there can be no doubt that in 

 many Rhynchophora the sac to be functional must be fully 

 extended, for the sessile — or even very minute (in Holony- 

 chus deflexus and H. gracilis, spp. n.) transfer -apparatus 

 is situate at its extremity, we may nevertheless doubt 

 whether in other cases anything more than a slight or 

 partial eversion occurs. From this point of view the 

 Otiorrhynchid forms assigned to the Celeuthetides are very 

 interesting, tor in some of them the length and tenuity of 

 the sac render a total eversion of the structure very im- 

 probable. Fig. 9 (Trigonops, or Heteroglymma, sp. n.?, 

 New Guinea) shows one of the longest and most slender 

 of these sacs; it contains a rather long curvate flagellum, 

 attached to the wall of the sac only at the base where it 

 is a little swollen and notched. It will be noticed that 

 there exists also in the interior of the body of the lobe 

 another structure which has all the appearance of being a 

 tube (fig. 9y) through which the slender flagellum may be 

 thrust and would then protrude sufficiently for intro- 

 mission. All that appears necessary in this case is for 

 the sac to be everted (or perhaps moved apically without 

 eversion) so that the flagellum passes into the director 

 and protrudes; possibly the director may then itself 

 move apically to a greater or less extent. 



The transfer apparatus of the sac reaches its greatest 

 complexity in the Scolytidae. Hence it attracted the 

 attention of Lindeman, who called the whole of the pieces 



