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Here we see the later life stages of several Painted Lady (Vanessa cardui)Butterflies.
Once the caterpillars are mature, they suspend themselves upside-down, by attaching a body part called the "cremaster" to a silken pad on the twig, much like the way Velcro works.
In about 1 day, the caterpillar sheds its final skin to complete the pupation process. Inside the pupa, the caterpillar has essentially liquified itself into a soup of cells. During the next 12-14 days, metamorphosis takes place - the cells are "re-arranged" and transformed into the adult insect. For most of this process, there is no visible change on the outside, but as the final few days approach, the developing adult butterfly can be seen through the semi-transparent pupal case. The butterfly's wing colors and pattern can be seen to darken. Finally, the fully developed adult separates from the pupal shell about an hour before it emerges, a process called "eclosion".
Once the adult emerges, it takes only a few minutes to expand its wings by pumping a body fluid into the wings' vein structure. After a couple of hours, the fluid dries and hardens, leaving the wings rigid enough propel it in flight.