130 
IV; 
THE MALAYAN PAPILIONIDA OR SWAL- 
LOW-TAILED BUTTERFLIES, AS ILLUS- 
TRATIVE OF THE THEORY OF NATURAL 
SELECTION. 
Special Value of the Diurnal Lepidoptera for enquiries 
of this nature. 
Wuen the naturalist studies the habits, the structure, 
or the affinities of animals, it matters little to which 
group he especially devotes himself; all alike offer him 
endless materials for observation and research. But, 
for the purpose of investigating the phenomena of geo- 
graphical distribution and of local, sexual, or general 
variation, the several groups differ greatly in their 
value and importance. Some have too limited a range, 
others are not sufficiently varied in specific forms, 
while, what is of most importance, many groups 
have not received that amount of attention over the 
whole region they inhabit, which could furnish mate- 
rials sufficiently approaching to completeness to enable 
us to arrive at any accurate conclusions as to the 
phenomena they present as a whole. It is in those 
groups which are, and have long been, favourites with 
collectors, that the student of distribution and varia- 
tion will find his materials the most satisfactory, from 
their comparative completeness. 
