142 PECKHAM. [Vol. 1, 



although the breast muscles are the seat of the highest activity, 

 breast plumes are the least frequent of all the forms of orna- 

 mental plumage. 



We may fairly say, then, that the humming-birds com- 

 pletely refute the proposition that there is any relation between 

 the development of color and accessory plumes and " surfaces 

 where muscular and nervous development is considerable. " If 

 the facts prove anything, it is that color and plumes appear on 

 all those parts of the body that are in view when the bird is on 

 the wing. This conclusion is irreconcilable with Mr. Wallace's 

 theory, but is quite in accord with that of Darwin, since the 

 humming-bird, in his display before the female, circles about, 

 rising and falling in the air in such a way that all his beauties 

 are well shown. Another important point in this connection is 

 that the courtship colors of the male are not found on the long 

 wing feathers. Professor Newton remarks, in his article on 

 humming-birds,''' that "the flight feathers are almost invariably 

 dusky; the rapidity of their movement would perhaps render 

 any display of color ineffective. " Mr. Poulton says that in 

 birds and insects we distinguish two kinds of flight ; in one it is 

 produced bj'^ an excessively swift vibration of the witigs, in the 

 other by a relatively slow, flapping movement. In the former, 

 including the humming-birds and the majority of insects, the 

 wings are quite invisible, owing to their rapid motion ; in the 

 latter, including the majority of birds and butterflies and 

 many moths, they can be easily seen. We find, as a general 

 rule, that the colors distinctive of sex are displayed on the wings 

 in the latter group, but are absent from the wings in the former. 

 Facilities for female observation are thus afforded by the 

 distribution of color. " f 



Relation Between Sexual Ornaments and Highly Nourished 

 Surfaces in Spiders. 



It is no less true in spiders than in birds that sexual orna- 

 ments are found where they can best be used in display, and 



*J£ne. Brit., Vol. XII, p. .3.5s. 

 t Colors of Animals, jp. SSli. 



