404 SEXUAL SELECTION. [Part II. 



has made, as he informs me, numerous trials, and finds no 

 exception to the rule, that all caterpillars of nocturnal and 

 retiring habits with smooth skins, all of a green color, and 

 all which imitate twigs, are greedily devoured by his birds. 

 The hairy and spinose kinds are invariably rejected, as 

 were four conspicuously-colored species. When the birds 

 rejected a caterpillar, they plainly showed, by shaking 

 their heads and cleansing their beaks, that they were dis- 

 gusted by the taste. 33 Three conspicuous kinds of caterpil- 

 lars and moths were also given by Mr. A. Butler to some 

 lizards and frogs, and were rejected ; though other kinds 

 were eagerly eaten. Thus the probable truth of Mr. Wal- 

 lace's view is confirmed, namely, that certain caterpillars 

 have been made conspicuous for their own good, so as to 

 be easily recognized by their enemies, on nearly the same 

 principle that certain poisons are colored by druggists for 

 the good of man. This view will, it is probable, be here- 

 after extended to many animals, which are colored in a 

 conspicuous manner. 



Summary and Concluding Remarks on Insects. — 

 Looking back to the several Orders, we have seen that 

 the sexes often differ in various characters, the meaning 

 of which is not understood. The sexes, also, often differ 

 in their organs of sense or locomotion, so that the males 

 may quickly discover or reach the females, and still oftener 

 in the males possessing diversified contrivances for retain- 

 ing the females when found. But we are not here much 

 concerned with sexual differences of these kinds, 



In almost all the Orders, the males of some species, 

 even of weak and delicate kinds, are known to be highly 

 pugnacious ; and some few are furnished with special weap- 

 ons for fighting with their rivals. But the law of battle 



33 See Mr. J. Jenner Weir's paper on insects and insectivorous birds, 

 in 'Transact. Ent. Soc' 1869, p. 21 ; also Mr. Butler's paper, ibid. p. 27. 



