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of one Insect or, if you prefer to call them so, in the closely allied 
species which replace each other in difterent faunistic provinces. 
Papilio clytia is represented on the Andaman Islands by a mono- 
morphic form resembling déssimilis, on the lesser Sunda Islands by 
another form also resembling dissimilis, and on the Philippines by 
a likewise monomorphic form which on the contrary corresponds 
to clytia, while in Ceylon, India, China, Siam, etc., both the 
dissimilis- and the clytia-form are found together. The two 
forms have long been considered by systematists as distinct spe- 
cies. But all the evidence derived from the cabinet specimens and 
obtained in the field point to these different looking Butterflies 
being the same Insect. The streaked dissimilis resembles a number 
of Danaids, while the dark c/ytia-form is similar to Eupleeids. 
On Borneo, Sumatra and Java, and extending northward to 
Palawan and Assam there occur two Papilios which were originally 
the Malayan representative forms of P. clytia, but are now specifi- 
cally distinct from it. These are Papilio paradoxus ZINK. (1832) 
and caunus WESTW. (1848). The former resembles Euplewva rada- 
manthus, and the latter, which varies to a great extent, mimics 
quite a number of different species of Zuploa. The two Papilios 
are in my opinion the same Insect. They are, however, so different 
in aspect that it will take a long time, I think, before systematists 
become convinced of the correctness of my interpretation. 
The kind of similarity instanced by Papilio clytia has not receiv- 
ed the attention it deserves, which may be due in a large measure 
to the circumstance that so few cases of this kind were known. 
The scarcity of instances, however, is more apparent than real. 
Faulty systematics must bear the blame. In descriptive entomology 
— and in other branches of biology as well — it has often been 
overlooked that the mere quantity of difference between two forms 
is not a safe guide in the discrimination of species. Polymorphism 
is much more frequent than we know as yet, especially in species 
which bear a likeness to members of other groups. Systematists 
at any rate learn this much from the theory of mimicry that 
thev must be cautious in their judgment as to specific distinctness 
when dealing with mimetic forms. Erycinids, certain genera of 
Lycænids, Castniids, certain American Hypsids which resemble 
Danaids, etc., should be studied from this point of view. 
The most striking heterotrope resemblance among all the 
Papilios is found in the Brazilian P. lysithous. The species consists 
