ttePlDOPTERA* 
581 
Under the general term variation Wallacd thinks that 
several different phenomena have been confounded. These he 
defines as follows : — 1st, simple variability; 2nd, polymorphism; 
3rd, local forms ; 4th> coexisting varieties ; 5th, races or sub- 
species ; 6th, true species. The Pesult of simple variability is 
the production of individual varieties, which occur almost con- 
tinually in some species, whilst others, nearly allied to these, are 
quite constant in their characters. Polymorphism (including 
dimorphism) consists in ^‘^the coexistence in the same locality 
of two or more distinct forms, not connected by intermediate 
gradations, and all of which are Occasionally produced from 
common parents.^^ The intercrossing of two of these forms 
does not produce an intermediate race, but reproduces the same 
forms. Thus Papilio merrinon (Linn.), S j has two forms of 
namely, P, ahceUs and P. achatis (Cram.) ; P. pammon (Linn.), 
S , has a $ nearly resembling it, but also two other forms, de- 
scribed as P. polytis (Linn.) and P. Yo^iutus (Cram.) ; whilst 
P. theseus (Cram.) has no less than four forms of ? — -one resem- 
bling the male, the others described as P . polyphonies (De Haan), 
P. antiphus (De Haan), and P. melanides (De Haan). Wallace 
refers to Some other etamples of this polymorphism in the 
females of Papiliotiides ; the different forms of tlie Malasiau 
species are also figured. Local forms or varieties occur in spe- 
cies of wide range where groups of individuals have become 
isolated in particular spots. P. agamemnon presents a good 
example of this. Under the denomination of coexisting va- 
riety Wallace means to indicate the existence of a slight but 
permanent and hereditary modification of form in company with 
the parent or typical form.^^ Races or subspecies are local 
forms completely fixed and specialized,^^ which may be, and are, 
regarded by many authors, and even by Wallace himself, as 
entitled to specific distinction. 
By applying these principles to the study of the Papilionides 
of the Eastern Archipelago, Wallace brings the number of spe- 
cies inhabiting those islands to 123, the distribution of which is 
sho^vn in an elaborate table (pp. 24-27) . The Indo-Malayan 
region, extending from Malacca to the Philippines, possesses 
61 species; the Austro-Malayan region, from Celebes to New 
Guinea and its dependencies, possesses 72 species ; so that only 
10 species are common to the two regions. This discrepancy 
between the Papilionides of the eastern and western parts of 
the archipelago is evidence in the same direction as the great 
number of forms occurring in the whole region. The whole of 
Africa possessed only 33 known species of these insects, and 
tropical Asia only 65. The whole of America south of Panama 
has only 120 species, or about the same number as here recorded 
by Wallace for the Malayan archipelago; but the area of South 
America is at 16ast 5,000,000 square miles, whilst the whole area 
