258 



THEORIES OF MIMICRY 



Another and equally interesting method is adopted by 

 certain tropical American Rhynchota Homoptera belong- 

 ing to the family Membracidae. In this remarkable group 

 the dorsal region of the first thoracic segment (the pro- 

 notum) 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 



Fig. 6. 



Fig. 



Fig 



5. — A Locustid from the Sudan, Myrmecophana fallax (Brunner), seen from 

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

 represented in black pigment, all other parts being light in colour and 

 presumably concealed. (From Brunner von Wattenwyl, Verhandl. d. k.-k. 

 zool.-botan, Ges. in Wien, Bd. xxxiii, 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. Cenlr.-Am., Rynch. Hotnopt., vol. ii, pi. 6, figs. 

 16, 16 A, & 17.) 



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 the body, which is 

 concealed. This change has been brought about, and 

 certain species of the group have their un-ant-like bodies 

 concealed under an ant-like shield. In other species the 



until so late as 1899 (David Sharp, F.R.S., Insec/a, vol. ii, Lond., 1899, 

 PP- 55 6 > 557. F»g- 269).— E. B. P., Oct. 1906. 



