THE CAUSE OF MIMETIC EESEMBLANCE. 



593 



in many different ways. To suggest an " accidental freak " as 

 the explanation shows an amazing credulity, only to be explained 

 by the bias whicb is ready to accept ant interpretation except 

 that afforded by tbe theory of natural selection. 



Fig. 6. 



Fig. 5. 



Fig. 5. — A Locustid from the Sudan, Mt/rmecopha7ia fallax (Branner), seen from 

 above and from the left side. On this insect the appearance of an ant 

 is represented in black pigment, all other parts beii:g light in colour 

 and presumably concealed. (From Brunner von Wattenwyl, Verhandl. 

 d. k.-t. zool.-botan. Ges. in Wien, Bd. xxsiii. 1883, pi. xv. figs. 1 a 

 & 1 b.) 



Fig. 6. — A Central- American Membracid (Rhynchota Homoptera) in which the 

 prothoracic shield resembles an ant. Thus the body of the insect 

 which is not like an ant is concealed by an ant-like shield. The 

 species is Heteronotus trinodosus as seen from above and the left side. 

 The upper of the two figures seen from the side represents a female, 

 the two other figures, males. (From W. W. Fowler, Biol. Centr.- 

 Am., Eynch. Homopt. vol. ii. pi. 6. figs. 16, 16 a, & 17.) 



Another and equally interesting method is adopted by certain 

 tropical American Rhynchota Homoptera belonging to the family 

 MemhracidoB. In this remarkable group the dorsal region of the 

 first thoracic segment (the pronotum) is of enormous size, 

 extending upwards and backwards so as completely to cover the 

 insect with the exception of the head, limbs, and wings. What 

 natural selection effects in the general body-form of other 

 insects, must here be effected, if it is to be of any value, in the 

 shield which is seen, and not in tbe body which is concealed. 



