I have some information on butterfly weights but not exact weights for the largest and smallest butterflies. However, I can make pretty good guesses. I have weights ranging from 0.3 gram for a large swallowtail to 0.04 gram for a small butterfly called the elf. My guess is that the female Queen Victoria Birdwing, the world's largest butterfly, would weigh 2 or 3 grams and one of the World's smallest butterflies, the Pygmy Blue, would weigh only a few thousandths of a gram.