butterflies of the "edge"

[John Grehan]

The following is a modified email request from Smruti Damania for
information regarding butterfly behaviour and ecology that I am not
sufficiently familier with
to provide answers. If anyone on the list would like to provide information
on these aspects and any pertinent literature I am sure she would be most
grateful. She is not a member of the list (although I will suggest that she
might
like to join) so please send responses to her email address (but also post on
the list if you think the points might be of general interest). John Grehan

From: "Damania" <smap at africaonline.co.ke>

I am a recent BSc. Zoology graduate from the University of Eastern Africa, 
Baraton. I am immensely interested in biological research and am an ardent 
butterfly enthusiast. While at the university, I had carried out several 
researches regarding the use of Lepidoptera as bio-indicators of different
biomes. 

According to my research, the greatest diversity of Lepidoptera were found 
in a sampling station that is a grassland patch lying at the edge of a
cultivated 
farmland. In my research, this 'edge' accounted for the highest distribution 
class of Lepidoptera. Also, another interesting fact was that while
sampling in the indigenous woodland biome of my study area, I found
aggregates of Milkweed butterflies(Amauris albimaculatus) to prefer a
certain area within the biome 
where trees had recently been felled; and a path lay alongside. 

I am curious as to why the preference for living on the 'edge' should be so. 
What exactly is it about the 'edge' that attracts butterflies to it? From my 
observations, I found that the boundary zone between different biomes was 
much more preferred than within the biome itself. Why opt for the 'boundary
line' 
or the 'edge' ,as you call it, in preference to an established, stable biome? 
I still cannot understand this, perhaps due to my limited knowledge on these
amazing creatures. 

In my research, A. albimaculatus, Papilio demodocus, Papilio dardanus, 
Papilio nireus and Vanessa cardui all show a preference to the 'edge'. 

What butterflies in America show a similar preference for the edge? 
Butterflies are still a relatively new field of study in my country, where 
conservation efforts tend to lean toward more economically profitable 
species.

Thankyou, 

Smruti. (Miss Smruti Damania, P.O. Box 975, Nakuru, Kenya)