638 Mr. D. Sharp and Mr. F. Muir on the Comparative 



Returning then to the Elaterid he will notice that the 

 change required to permit the tegmen in that form to 

 ride over, or cloak, the median lobe consists in the first 

 place of an elongation of the connecting membrane between 

 them. If this take place and the liberated lateral lobes 

 be approximated dorsally, we have in fact the essentials 

 of the arrangement as we find it in Cucujidae. We might, 

 then, conclude that it is permissible to derive the Cucu- 

 joidea from the Byrrhoidea. When, however, we turn to 

 consider whether such a change has ever actually occurred, 

 we must ask ourselves whether it is probable that an 

 aedeagus that is functioning as an organ of one layer 

 would change into a structure that functions as a two 

 layer arrangement. We think the answer would be that 

 in the early conditions of the genital tube such a change 

 might occur, but that after the aedeagus had attained a 

 considerable development nothing of the sort is at all 

 probable. 



We now return to the consideration of the Phyto- 

 phagoidea. If a well-developed Cerambycid aedeagus (say 

 one of Cly tini) be compared with Cucujus it will be noticed 

 that in the position occupied by the "lateral lobes" (if 

 really such) of the latter there is in the Clytus a divided, 

 or rather cleft, process resembling the Cucujus lobes, and 

 it would appear therefore that if the Cucujus possesses 

 lateral lobes so also may the Clytus. 



A further examination of a variety of forms of the two 

 series produces the gravest doubts. In the Cucujoidea 

 the lateral lobes are either articulated at the apex of the 

 tegmen, or if the articulation be absent, the single part 

 has the appearance of being two parts combined (cf. 

 Helota). But in Phytophagoidea (at any rate in Ceramby- 

 cidae) there is never any articulation of the apical processes 

 of the tegmen, and the comparison of a series of forms 

 suggests that the bilobed state of the apex of the tegmen 

 (or cap-piece) may be the result of progressive emargination 

 of what was originally a single piece.* In that case the 



* In the Cerambycidae (especially marked in genus Phrissoma), 

 there is a ridge on the underface of the divided cap-piece giving an 

 illusory appearance of articulation of the two lobes. In the Curcu- 

 lionidae the appearance is different : there are often two separated 

 lobes (the "papilla" of Hopkins in Fissodes), and in Euplioluti the 

 lobes are widely separated (this point is not well shown in our 

 fig. 222((), while in some other Rhynchophora there is a single 

 median prolongation of the cap-piece. None of these cases is similar 



