Admirals in the Nettle Patch

I saw a red admiral in the prairie over the weekend. They are seen from March to November and mostly during the summer. I enjoy the fact that both sides of the wings are very different colors. It’s so good to see another butterfly!

Admirals in the Nettle Patch
by Anita Carpenter

When the days turn warm and sunny, I know that butterfly season has begun. I now eagerly await the arrival of a new generation of the well-known, long-distance migrants known as monarch butterflies. But the monarch is not the only butterfly to return. Red admiral butterflies also migrate into the state, though arriving without the fanfare that the monarchs receive. Unlike the monarchs, in some years red admirals are numerous, and in other years they may be scarce.

Red admirals (Vanessa atalanta) are easy to identify, that is, if the butterfly ever stops flying long enough to bask with wings open. Then a bright red-orange band that bisects the velvety brown upper wings and a second red-orange band that highlights the trailing edge of the hind wings are readily seen. Several small white spots dot the forewing tips. Its underwings are mottled in shades of brown, gray, tan, and black, providing the perfect camouflage when the butterfly rests with closed wings upon a tree trunk. In flight, red admirals appear black. Their flight is fast, erratic, and difficult to follow.

The host plant upon which red admirals lay their eggs is a plant most people find objectionable and would not welcome into their yards. The plant has stinging or urticating hairs that inflict an unpleasant and irritating tingling or stinging sensation on the skin. As its name implies, this plant is stinging nettle (Urtica dioica).

When a male red admiral is searching for a mate, he sets up a territory, which he vigorously defends by patrolling around its perimeter. Females only mate with males who have established territories.

After mating, females deposit light green eggs singly on the upper surface of a stinging nettle leaf. Within days, a tiny, black caterpillar, which is covered with tiny spines, hatches. Using silk extruded from its mouth, each caterpillar pulls the leaf edges together and silks it shut to construct a leaf shelter. The caterpillar lives safely within the folded leaf and feeds on the nettle leaf. After three or four molts, a fully-grown spiny black caterpillar, decorated with a light yellow “racing stripe” along its sides, leaves its leaf shelter and crawls off the plant. It finds a spot to pupate and emerges as a free-flying butterfly.

A good clue to finding a caterpillar is to look for the folded-leaf shelters. You can carefully open the leaf to find the caterpillar inside, but please close the leaf when done to protect the caterpillar. Caution: remember that handling the leaf may irritate your fingers.

A second generation of red admirals may emerge in August. These individuals overwinter as  butterflies. Because red admirals are not adapted to winter, they may perish or do a reverse migration and head for the southern states.

Red admirals may undertake spectacular mass movements in autumn or in spring. The year 2001 was the last year an extraordinary movement occurred. Red admirals were everywhere, and I remember a mature flowering basswood tree covered with red admirals. It was an extraordinary sight.

So, venture out to look for red admirals. Look near a stinging nettle patch. Maybe you’ll be fortunate enough to find a butterfly and/or a folded-leaf shelter. Will this be a great year to find red admirals in good numbers, or will it be a year when they will be missing? We’ll have to patiently wait to find out.@

The Home page image for this blog post shows the red admiral (Vanessa atalanta) butterfly on New England aster (Symphyotrichum novae-angliae).