competition for food, literature question

[Kondla, Norbert FOR:EX]

I recently read a stated concern about butterfly species x competing with
another species for food supply.  I am a little sceptical about this view.
Even when dealing with populations of one butterfly species, I do not recall
running across any empirical data to suggest that food supply is any kind of
real limiting factor in butterfly abundance (of course in mathematical
models anything can be turned into a limiting factor).  Have I missed some
key literature ? Anyone out there that can share some references with data
to show population limitation due to food supply (amount). Conceptually I
could see such a thing in the case of a butterfly population that is
dependent on one endangered host plant but darned if I can think of a
documented example.  Thanks in advance for sharing your knowledge.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Norbert Kondla  P.Biol., RPBio.
Forest Ecosystem Specialist, Ministry of Environment
845 Columbia Avenue, Castlegar, British Columbia V1N 1H3
Phone 250-365-8610
Mailto:Norbert.Kondla at gems3.gov.bc.ca       
http://www.env.gov.bc.ca