14 MR. A. R. WALLACE ON THE PAPILIONIDiE 



rather than diminishes. And it must be remembered that the naturalist is rarely Likely 

 to err on the side of imputing greater indefiniteness to species than really exists. There 

 is a completeness and satisfaction to the mind in defining and limiting and naming a 

 species, which leads us all to do so whenever we conscientiously can, and which we know 

 has led many collectors to reject vague intermediate forms as destroying the symmetry of 

 their cabinets. We must therefore consider these cases of excessive variation and insta- 

 bility as being thoroughly well established ; and to the objection that, after aU, these cases 

 are l)ut few compared with those in which species can be limited and defined, and are 

 therefore merely exceptions to a general rule, I reply that a true law embraces all 

 apparent exceptions, and that to the great laws of nature there are no real exceptions — 

 that what appear to be such are equally results of law, and are often (perhaps indeed 

 always) those veiy results which are most important as revealing the true nature and 

 action of the law. It is for such reasons that naturalists now look upon the study of 

 carieties as more important than that of well-fixed species. It is in the former that we 

 see natiu'e still at work, in the very act of producing those wonderful modifications of form, 

 that endless variety of colour, and that complicated harmony of relations, which gratify 

 every sense and give occupation to every faculty of the true lover of nature. 



VmHation as specially/ influenced hy Locality. 



The phenomena of variation as influenced by locality have not hitherto received much 

 attention. Botanists, it is true, are acquainted with the influences of climate, altitude, and 

 other physical conditions in modifying the forms and external characteristics of plants ; 

 but I am not aware that any peculiar influence has been traced to locality, independent 

 of climate. Almost the only case I can find recorded is mentioned in that repertory of 

 natural-history facts, ' The Origin of Species,' viz. that herbaceous groups have a tendency 

 to become arboreal in islands. In the animal world, I cannot find that any facts have 

 been pointed out as showing the special influence of locality in gi^'ing a peculiar fades 

 to the several disconnected species that inhabit it. What I have to adduce on this 

 matter wdll therefore, I hope, possess some interest and novelty. 



On examining the closely allied species, local forms, and varieties distributed over the 

 Indian and Malayan regions, I find that larger or smaller districts, or even single islands, 

 give a special character to the majority of their Papilionidai. For instance : 1. The 

 species of the Indian region (Sumatra, Java, and Borneo) are almost invariably smaller 

 than the allied species inhabiting Celebes and the Moluccas ; 2. The species of New 

 Guinea and Australia are also, though in a less degree, smaller than the nearest sijccies 

 or varieties of the Moluccas ; 3. In the Moluccas themselves the species of Amboyna are 

 the largest ; 4. The species of Celebes equal or even surpass in size those of Amboyna ; 

 5. The species and varieties of Celebes possess a striking character in the form of the 

 anterior wings, different from that of the allied species and varieties of all the surround- 

 ing islands ; 6. Tailed species in India or the Indian region become tailless as they 

 spread eastward through the archipelago. 



Having presei-ved the finest and largest specimens of Butterflies in my own collection, 

 and having always taken for comparison the largest specimens of the same sex, I believe 

 that the tables I now give arc sufficiently exact. The differences of expanse of wings 



