The spiny elm caterpillar is the larval stage of the mourning cloak butterfly.
The spiny elm caterpillar (Nymphalis antiopa) belongs to the category of "stinging caterpillars." When full grown, this two-inch-long caterpillar is covered with bristles. Its body is black with numerous white flecks and a row of red spots down the back; the prolegs are red.
The spiny elm caterpillar is the larval stage of the mourning cloak butterfly, a desirable species for the butterfly garden. The caterpillar feeds on the leaves of elm, willow, hackberry and cottonwood, rarely causing significant damage. In some parts of the country the caterpillars are seen in spring, but in some areas a second brood may be seen in late summer. The mourning cloak butterfly is also one of few butterflies to overwinter in the adult stage.