(Portland, OR) -- The Oregon Zoo has released over 13-hundred rare Oregon silverspot larvae along the coast to grow the butterfly population. They thrive on early blue violets, and the plants only grow in large enough numbers at Nestucca Bay and Saddle Mountain. Invasive weeds and forest changes have reduced the early blue violet growing areas. The Zoo captures silverspots during the summer, they lay eggs that become caterpillars, and once they become larvae, they're released to become butterflies.