Anatomy of the Male Genital Tube in Coleoptera. 637 



We will now turn to the point for the elucidation of 

 which this digression has been made, viz. the value of 

 lateral lobes in the consideration of phylogenetic points. 



The lateral lobes extend in the longitudinal direction, 

 while the various invaginations are the result of trans- 

 verse creasings. That lateral lobes can be much modified 

 in their position is clear. There is no doubt that they 

 can be brought more to the ventral surface or more to 

 the dorsal surface, and there is no doubt that they can be 

 approximated, made contiguous or even conjoined. These 

 facile changes, whether great or small morphologically, 

 have no doubt been actually limited, and when we recol- 

 lect that there must always have been such an agreement 

 between the male and the female parts of the genital 

 conduit that good viability was invariably preserved, we 

 must adopt the view that may be summed up in the words, 

 " the less change the better." 



Are lateral lobes present in all Coleoptera ? And if 

 they are not to be definitely seen in some forms is this 

 to be attributed to original absence or to secondary 

 modification ? 



In the Byrrhoidea lateral lobes are a conspicuous feature. 

 So are they also in Caraboidea, with a slight difference in 

 position. They are present in tlie Staphylinoidea in a 

 variety of shapes and modifications of a very interesting 

 character. They also exist in Malacodermoidea, in Tene- 

 brionoidea and in the Scarabaeoidea. 



In the Cucujoidea lateral lobes appear to be absent. 

 But there are frequently present apically and on the 

 middle of the tegmen two articulated processes that may 

 be considered to be their homologues by process of a 

 change to explain which we must make another brief 

 digression. 



If the reader will examine one of the typical Byrrhoidea, 

 e, g. a large Elaterid, he will note that the tegmeji is so 

 attached to the median lobe as to permit of little or no 

 independent movement of the two ; they work, in fact, as 

 a single layer. Let him then take a Cerambycid aedeagus 

 (the members of which are all conformable as regards the 

 point in question), and he will find the reverse condition 

 displayed, the median lobe and tegmen being so arranged 

 as to permit of a play of the former through the latter, 

 the two parts function as two layers, one cloaking the 

 other. 



TRANS. ENT. SOC. LOND. 1912. — PART III. (dEC.) U U 



