This is a Painted Lady butterfly (not endangered) that I grew at home from larval stage - you can grow them too by buying caterpillars on the Insect Lore website (Cup of Caterpillars - Insect Lore), this helps ensure that populations remain healthy because within your house there are no predators, competitors, or natural hazards (such as temperature).
More than 20 species of butterflies and moths have been listed as endangered by the US Fish and Wildlife Service including the critically endangered Monarch Butterfly.
Female butterflies will ONLY lay their eggs on their specific host species which is different for every species of butterfly (this is Milkweed for Monarchs). If there is no Milkweed present then the female will not lay her eggs and as such there will be no new Monarch caterpillars.
In addition, the pollen of Bt Corn, which is a genetically modified form of corn and produces a natural pesticide, is killing Monarch caterpillars. If the pollen of this corn lands on the leaves of a Milkweed plant, the new caterpillars will eat that pesticide after they hatch from their eggs, and die.
There has also been a huge decline in the amount of Milkweed plants in the USA with similar things happening for many other host plant species.
What else do you think you can do to help rejuvenate butterfly, and specifically Monarch butterfly populations? Could you grow your own Milkweed plant or other butterfly host species plant at home to encourage the butterflies to lay their eggs? How can you set up a butterfly garden?