Hopefully the Butterfly photography will improve as the summer progresses but for now the populations seem to be below normal. If I were to guess the cause I would suspect the cool wet spring. Our temperatures have averaged below normal with rainfall above average until July ushered in a drying spell.
Farmers may hate thistles but make no mistake Butterflies love them. When looking for butterflies images one will never go wrong wondering about in a patch of thistle. Contact with the sharp needles can be uncomfortable but the beautiful blossoms combined with the brilliant colors of butterflies is a combination hard to beat.
These images were captured with a 100-400mm Canon lens & 25mm Kenko extension tube. I have found this to be a useful combination as the 400mm allows one to maintain a comfortable distance that does not alarm the butterflies while still capturing a suitably large image. A tripod is a necessity with this combination as it is virtually impossible to maintain focus otherwise because of the extremely shallow depth of field.