It kind of depends on what kind of images you want to create and how far you have to carry all of the equipment
I would expect most of the orchids will be growing in trees so a fast 70-300mm macro that will go to 1:2 would be my first choice and this would work well for butterflys as well. It would be even better to add a twin flash cross polarized setup. Being able to have the flashes quite a distance from the camera would be beneficial.
If you'll be baiting the butterflys (putting sugar solution on flowers), then you can use multiple flashes to get both the subject and the background lighted.
is a good macro reference site