( 449 ) 



standing at right angles to the veins ; if Eimer had assumed that the original 

 pattern of the wings consisted of " longitudinal " bands running in the direction 

 of the veins,* he would have arrived at a " jireponderance " of i\\& female sex. 



The degree of divergency is, in many subspecies, so minute that the peculiarity 

 would escape even a skilled eye but for a carefully working systematist having 

 drawn attention to it, and having fixed, so to say, the minute peculiar character 

 by naming the subspecies. Romanes has severally referred to minute specific 

 characters in order to confute Wallace's opinion that all specific characters are 

 useful; as specific characters are only higher degrees of development of subspecific 

 characters, the question whether subspecific characters have originated and are 

 accumulated by Natural Selection is no less important than the same question in 

 respect to sjiecific characters. Dixon t and Allen % give ample illustrations of the 

 question as regards birds. Of Lepidoptcra we mention, out of hundreds of cases, 

 only two : Papilio nomius has a western subspecies (Ceylon to Assam) and an 

 eastern subspecies (Burma, Tenasserim, Tonkin, Hainan) which are constatitb/ 

 differentiated by one minute character, namely a brown line situate in the eastern 

 form on the praecostal vein on the underside of the hindwing, which short and thin 

 line is absent from the specimens of the western subspecies ; that this distinguishing 

 character is indeed minute will be admitted if we add that, though it is the only 

 constant difierence of the two subspecies we can find, it has never been mentioned 

 by any specialist until 1895, in Mr. Walter Rothschild's Revision of the Eastern 

 Papilios.§ Papilio agamemnon argynnus from the Kei Islands and P. agamemnon 

 neopommeranius from Neu-Pommern differ from all the other subspecies of 

 agamemnon in the hiudwings being above nearly devoid of markings, which renders 

 the two subspecies extremely similar ; but there is one constant character, which 

 can easily be perceived with the help of a lens, that distinguishes neopommeraniui 

 and argynnus : in neopommeranius the spots of the median row of the forewing 

 beneath are scaled all over, while in arqi/nnus the outer portion of each spot is 

 scaleless. Though nobody can very well entertain the opinion that such differences 

 are due to the direct action of Natural Selection, one can evade the weight of the 

 minute distinguishing characters by the assumption that these minute characters are 

 correlated to some other, unknown, character which is of a useful kind. Lepidoptcra,, 

 however, furnish us with the means to repudiate this evasive answer. All those 

 species which are said to be mimetic, and which have been quoted again and again 

 as excellent illustrations of the marvellous effect of Natural Selection, have certain 

 characters of colour or form which are attributed to the direct (not indirect) 

 influence of Natural Selection. Now, if such a character varies geographically in 

 the mimetic species and at the same locality in the imitated species by minute 

 degrees, the minute difiference between the geographical forms of the mimetic 

 sjjecies ought logically also to be attributed to the direct action of Natural Selection. 

 Such cases are, however, not rare among insects. We refer, for the sake of illus- 

 tration, to one of the most striking examples of mimetic adajitation. Papilio 

 caunus of the Malayan region has a style of marking (piite unusual for a Papilio, 

 and resembles another, nauseous, butterfly, Euploea rhadamanthus, to a surprising 



* According to Eimer, the costac and rows of punctures on the elytra of beetles are transverse, while 

 the bands (iif Ciramhijciflae, Cantharidae, etc.) which stand at right angles to those rows, and which are 

 often continuations of the transverse bands of the sterna and abdomen, must be called longitudinal. 



t Erolntiim without Natural Sdrction, London, 1885. 



X On the Mammalt and Winter Birds af Jiast Florida, in Bull. Miis. Comp. Zool. II. 1871. 



§ Nov. ZOOL. 18'J5. p. 422. 



