The Pentax Papilio models are by far the best for close-focus work because they focus down to 18 inches (45 cm) or less, correct for parallax (thus maintaining a truly binocular view at close distances--a unique feature), are very well made, and cost only $110. Their only weakness is that they are not especially bright. These are the model to get unless you are looking for something that is better suited for full-time dual use as a birding binocular. I have the 6.5x21 model and use them when I am exclusively butterfly watching.
The Brunton Epoch 7.5, 8.5, and 10.5x43 models all focus to 3 feet (92 cm), but they are not nearly as comfortable to view through at close distances as the Pentax because the left and right views don't overlap (especially in the higher powers). These are also EXTREMELY expensive given that they are optically mediocre compared to similarly priced models from Swaovski, Leica, and Zeiss, and cheaper models from Nikon.
The Eagle Optics 8x32 Platinum Ranger focuses down to just over 3 feet (92 cm), but because it has no parallax correction, it isn't as comfortable as the Pentax. The poor optical quality outside the very center of the field compromises the view at close ranges since the image overlap of the left and right fields is not great enough to allow center-field overlap. I consider these a bit overpriced at $300-$350 given their overall optical quality.
The best full-size butterfly bino is the Bausch & Lomb 8x42 Elite (waterproof model versions). It is no longer made, but you might be able to find a used one for a few hundred dollars. It focuses down to just over 4.5 feet (1.37 m) and has excellent image quality at all distances.
My favorite bird/butterfly combo binocular is the Zeiss 8x32 FL. Mine focuses down to 5 feet (1.52 m), which is closer than any of the other currently manufactured premium binos as far as I know. It is superb but pricey.
--AP