a basic, probably dumb question I haven't found the answer to yet.

[Nigel Venters]

My experience in Central Africa show that butterflies are attracted to both
colour and scent. A very powerful attractant is rotting banana (Especially
Charaxes ssp) a walk through the forest with a bucket full of banana bait
usually brings a good number of Charaxes flying round you and the bucket
before you get the chance to walk more than a few yards (or put up traps).
Leopard droppings are also a great attractant, but male Charaxes only!
Often you will find papilio ssp on damp mud (males only) and urine enhances
the attractiveness of the mud. Male Papilios of all species are attracted
to these areas visually, either seeing other papilios feeding (any colour
or species) or by putting down some coloured cards, yellow or blue both
work well.   Passing male Papilios will halt in their tracks as soon as
they spot others feeding. I also presume that to a lesser extent scent
plays a part too, or the first Papilio wouldn't have found the spot in the
first place. Of course Papilios also are very keen flower feeders, I assume
the same attraction follows, colour followed to some extent by scent also?
Nigel