( Ixxiii ) 



are the Longic.ornia and the Ileteromera : the Loncjicornia are 

 a well-marked group, and as they appear to have been some of 

 the latest of the Coleoptera, it is not perhaps surprising that 

 they imitated more ancient groups ; but the Heteromera, or 

 some of them, appeared at a very early date, and such an 

 explanation will not hold in their case. It is, however, very 

 probable that the Heterotnera do not form a unit at all. The 

 chief character by which the members of the group are dis- 

 tinguished, and from which it takes its name, is the fact that 

 the anterior and intermediate tarsi are S-jointed and the 

 posterior tarsi 4-jointed ; there ai"e, however, many instances 

 of heteromerous beetles in other large sei-ies, as, for instance, 

 Anisotoma, Acritus, the male of Bhizop/iagus, etc., so that the 

 character by no means holds good in all cases, and there is 

 no other upon which the groups can be strictly defined. The 

 Tenehrionid;v, Lagriida' and CistelidcT, with their closed coxal 

 cavities, may perhaps be considered a natural group, but it 

 is obvious that several of the other Heteromerous families 

 have very little, if any, connection with one another, and 

 might, with better reason, be assigned to other groups, of 

 which they are now, perhaps, merely considered the mimics. 



I must now bring this address to a close : the more we study 

 the questions involved in the general subject which we have 

 been discussing, the more, I think, does it seem possible that 

 several causes may have been at woi^k to produce the evident 

 results. There is no reason why the explanation should be the 

 same in all cases : doubtless there are many undesigned coinci- 

 dences in nature, and contjnuous and discontinuous variation 

 may both be working out similar ends : there is much to be 

 said for the gradual influence of what Dr. Dixey calls " mimetic 

 attraction," * and, more than many think, for sudden changes 

 without intermediate links. Tiie geological record is admittedly 

 very imperfect : in fact, we have hardly done more than scratch 

 upon its surface ; but the seemingly abrupt appearance of 

 the many elaborately perfected families of Coleoptera, with- 

 out any transitional forms, appears at present to be an 

 inexplicable problem. 



I cannot conclude without saying how much pleasure it 

 ^ Trans. Ent. Soc. 189G, I. 65 ; 1897, III. 317. 



