The wing-span of this butterfly is 3 – 3 3/8 inches. Dorsally, it is blackish with a brilliant blue iridescence. The forewing has 4 small, orange submarginal spots which tend to fade with age. Ventrally, both wings have 2 rows of pale blue broken lines around the margin and orange and pale spots around the bases of the wings. In addition, there is a row of square, orange submarginal spots on the hindwing. The hindwing has a squarish shape. The mature caterpillar is approximately 1 1/2 inches long and is a bird-dropping mimic. The foreparts are humped and the body has a lumpy looking appearance. It has a brown and cream-colored blotchy coloration, and 2 bristly “antlers” behind the head. The Viceroy caterpillar is very similar, but the antlers are slightly less clubbed.
This is a common butterfly in midsummer. It especially likes to mineralize from damp soil and can be numerous along Gifford Road after a rain.
The Red-spotted Purple mimics the poisonous blue Pipevine Swallowtail (without the tails) thereby giving it protection from birds. The Admiral caterpillars which include Red-spotted purple and Viceroy (subfamily Limenitinae) are readily recognized as they are the only horned bird-dropping mimics. Larval hostplants include cherry, oak and poplar.
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