Cecropia Surprize

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by Neil Carleton

Although late arriving for the Annual General Meeting of the Mississippi Valley Field Naturalists on May 17, I had a remarkable sighting to share during the banquet that followed. What distracted me from getting ready on time were two moths with a wingspan the size of my hand. As I pushed the wheelbarrow past the cluster of dogwoods growing at the end of our small backyard pond, some movement caught my eye. When I stopped to look carefully, the crescent eyespots of a female and a male cecropia moth (Hyalophora cecropia) were looking back at me.

Cecropia moths, with wingspans ranging from 110 to 150 mm, have distinguishing crescent eyespots on their wings

Not long before I noticed this mating pair, the male would have been flying upwind to the source of a pheromone released by the female. Males can locate a potential mate from 5 or 6 kilometers away. Once he found the female and landed beside her, they would have mated without courtship.

Yesterday was a fine time to hang a few loads of wet laundry on the line. As I placed my empty basket in the shade, there, almost at my fingertips in the basswoods, was the large female cecropia again. She hadn’t moved far from where I first saw her, and was resting in the dappled light that filtered through the stems and leaves. As I crept up ever so carefully to take a few photos, she rewarded me for my interest by moving slightly so the sunlight caught her wings.

The crescent eyespots and rich colours of this female cecropia moth are bright in the dappled sunlight. The feathery antenna are also prominent in this view.

   If a cecropia caterpillar escapes a wide range of feathered predators, it spins a large, tough cocoon to overwinter. A valve at one end allows the moth to emerge in the spring. This cocoon, hidden in the dogwoods by our backyard pond, is where the female would have pupated and emerged as an adult. Females stay close to their cocoons until mating, then, in their remaining 4 or 5 days of life, they lay 200-300 whitish oval eggs on the underside of plant leaves that are eaten by the caterpillars.

Although the outside of a cecropia cocoon is tough and rough, the inside is spun with silk. This example, hidden in the dogwoods, includes some of last year’s leaves.