DIVERSE CAUSES OF RESEMBLANCE 261 



that there is something advantageous in the resemblance 

 to an ant, and that Natural Selection has been at work. 

 The phenomena do not merelydisprove all other suggested 

 causes of change ; they constitute the most powerful 

 indirect proof of the operation of Natural Selection. 



1 2. The Reseutd lances within the Limits of the Order are 

 also produced in the most Diverse Ways. 



Illogical as I believe the position to be, it is quite 

 possible that many observers may concede the force of 

 the argument concluded above, and yet continue to hold 

 that the resemblances within the Order are produced by 

 External or perhaps by Internal Causes. It can, how- 

 ever, be shown that the very same conditions which were 

 true in the wider group are also found in the narrower. 

 Even within the Order itself resemblances are produced 

 in very diverse ways, although minute examination is 

 sometimes necessary before the essential difference which 

 separates them can be revealed. 



Certain Longicorn beetles resemble weevils, the Curcn- 

 lionidae being, so it is believed, specially defended by 

 their extremely hard chitinous covering. The weevils 

 closely resembled by such Longicorns as Doliops curcic- 

 lionoides and D . geometrica have short antennae ending in 

 a knob. The antennae of the Doliops are nearly three 

 times as long ; the resemblance to the weevil being 

 produced by a dilatation of the third joint, which repre- 

 sents the knob, while all the joints beyond are of such 

 excessive fineness that they are almost invisible. The 

 strong resemblance of the Longicorn Estigmenida varia- 

 bilis to Estigmena chinensis, belonging to the Hispidae 

 (Phytophaga), is brought about in a similar manner, as 

 was pointed out by C. J. Gahan. In this case about one- 

 third of the length of the Longicorn's antenna is concealed 

 by its extreme fineness, while the apparent terminal 

 thickening is produced by hairs at the end of the stouter 

 basal section. 



In these examples, kindly shown me by Mr. Gahan, 

 neither the theory of External nor that of Internal Causes 

 is of any avail. It is impossible to believe that the 



