On October 17, 2005, our class conducted an experiment with Danaus plexippus butterflies. We took a Danaus plexippus butterfly and measured the left wing span from the tip of the wing to where the wing meets the thorax. We also determined the sex of each butterfly. Our research revealed that the male had a dot on its wing and the female did not. We collected data on 31 butterflies. We discovered that there is no difference in size between male and female Danaus plexippus butterflies.