170 PROCEEDINGS OF THE ACADEMY OF [Jan., 



show the hopelessness of any attempt to bring all the examples of 

 sexual dimorphism under any single law except one which expresses 

 the two principles explained on p. 169. The complexity of the 

 subject is still further increased by the fact that different elements 

 in the pattern of a species will often fall into more than one class. 

 Thus Dixey has maintained that the female of Argynnis diana 

 Ijelongs to the third of the above classes except as regards "the 

 large expanse of blue ground colour," which is mimetic and belongs 

 to the first class (7, p. 106, footnote). 



In his later paper (34) Dr. Skinner has still further developed 

 his objections to any special interpretation of the various classes 

 of sexual dimorphism in butterflies. He speaks of velvety patches 

 <on the fore wings of male Satyrince and brands on the wings of male 

 Hesperidce. The researches of Fritz Miiller (39) show that these 

 structures are scent-producing organs, and there is no doubt that 

 they are of use in courtship, or epigamic. The law that would be so 

 <3omprehensive as to explain at once an epigamic scent-patch, the 

 more rudimentary anterior foot of a male Nymphalid and the mimetic 

 pattern of its female, would be so very general that it would not 

 -carry us any distance in the attempt to understand each of these 

 different facts. 



Concerning Papilio glauciis glaucus and its dark turnus female 

 (I adopt Rothschild and Jordan's synonymy, 30, p. 582), which some 

 naturalists at least regard as mimetic of Ph. philenor, Skinner says 

 (34, p. 25) in criticism of Edwards: "There is also an assumption 

 to which I take exception. Does anyone know which one [the dark 

 or the male-like female] appeared first and why?" With regard 

 to the last word "why," Edwards had expressly disclaimed know- 

 ledge, for he speaks of "some unknown influence" causing the appear- 

 ance of the black female, and we can say no more than this to-day. 

 With regard to the other part of the question, I think it may be 

 shown that Edwards took the reasonable view in supposing that the 

 dark female appeared later than the male-like one. The male 

 pattern is shown to be ancestral, because it l^-^ars an intimate relation- 

 ship to the pattern of other aUied Papilios. 



This is the ai'gument used by Scudder (6, p. 534) in the following 

 joassage: "In Jasoniades glaucus, where we sometimes have a 

 black female, it is more difficult to decide what should be considered 

 the normal color, owing to diversity of view upon the relationship 

 of many of the swallowtails; but, to judge only from those agreed 

 hy all to be most nearly allied to it, there can be no question whatever 

 that the striped character prevails." 



