Thanks for the comments guy. Butterflies do seem to favour Pentax, they kept landing on our cameras

Mike, these butterflies were really not worried by us. Maybe the fact that there was no wind helped. It was also very humid. I mostly worked with the 50 macro, getting really close. For some of those (the ones shot from the side, mainly) the 300 mm lens helped a lot. The 17-70 "standard" lens was used for a little bit of everything, it's no macro but it's close focusing. This arsenal got all bases covered for me during that outing. Maybe you could try a long tele if your butterflies scare easily.