40 



GENERAL PRINCirLES OF ZOOLOGY 



females, since these are less numerous and have heavier bodies than the 

 males. So there arises a sexual dimorphism. If lire mimicing species 

 have a wide distribution, ditferent bad flavored species may be mimicked 

 in different parts of the range. The females of Papilio mcrops mimic, 

 in different regions, Daiiais chrysippiis, Amaiiris cchcria and .1. mavias, 

 wliile tlie males have the same appearance throughout the whole habitat. 



Fig. 14. — 17, Myi^nimia aviculus, a wnsp imilatcil by a beetle, h, CoIi'hi>rlioiiibiis /ijsl'li- 

 lipciiiiis (after Wallace). Three-fourths natural size. 



Sexual Selection is a special phase of natural selection, diiefly 

 observed in birds and hoofed animals. For the fulfilment of liis se.xual 

 instincts the male sSeks to drive his competitors from the field, eillier in 

 battle or by impressing the female by liis charms. With strong \vings and 

 with spurs the cock maintains possession of Ms flock, the stag by means 

 of his antlers, tlae bull with his horns. The male birds of paradise win the 

 favor of the females by means of beautiful coloring; most singingdjirds, 

 by means of song; many species of fowl, by peculiar love-dances. Since 

 all these characters belong chiefly to the male, and since only exception- 

 ally are they inherited by the female (and even then arc less pronounced), 



