146 THE MALAYAN PAPILIONIDZ AS 
these distinct forms breed independently, and are never 
reproduced from a common parent, they must be con- 
sidered as separate species, contact without intermix- 
ture being a good test of specific difference. On the 
other hand, intercrossing without producing an inter- 
mediate race is a test of dimorphism. I consider, 
therefore, that under any circumstances the term 
“variety ” is wrongly applied to such cases. 
The Malayan Papilionide exhibit some very curious 
instances of polymorphism, some of which have been 
recorded as varieties, others as distinct species; and 
they all occur in the female sex. Papilio Memnon 
is one of the most striking, as it exhibits the mixture 
of simple variability, local and polymorphic forms, all 
hitherto classed under the common title of varieties. 
The polymorphism is strikingly exhibited by the fe- 
males, one set of which resemble the males in form, 
with a variable paler colouring; the others have a 
large spatulate tail to the hinder wings and a distinct 
style of colouring, which causes them closely to resem- 
ble P. Coon, a species having the two sexes alike and 
inhabiting the same countries, but with which they have , 
no direct affinity. The tailless females exhibit simple 
variability, scarcely two being found exactly alike even 
in the same locality. The males of the island of Borneo 
exhibit constant differences of the under surface, and 
may therefore be distinguished as a local form, while 
the continental specimens, as a whole, offer such large 
and constant differences from those of the islands, that 
I am inclined to separate them as a distinct species, to 
b 
