The biggest moths

kw: moths, lepidoptera

I got a surprise when I stumbled across the information that this is the largest moth in North America. It is the Black Witch, though if the species had been named for the female, it would be called the Brown Witch; there is a significant color difference between the sexes.

The Black Witch, Ascalapha odorata, is the largest North American moth, with a wing span of 11-15 cm (4.4-6 in). It is found throughout the country, though a sightings map at Butterflies and Moths of North America shows it has been seen in scattered locations, coast to coast and from south to north, rather than "just about everywhere". This is probably because it is nocturnal. I suspect it is as widespread as the familiar yellow swallowtail butterfly, which I've seen in every US state I've lived in (seven states).

Prior to this morning, I thought the largest moth in the US was the Ailanthus Silk Moth, Samia cynthia, but its wing span is a trifle less: 10-14 cm (4-5.5 in).

Even if this silk moth were larger, it is not a US native; it was brought here from China in an effort to establish an American silk industry. That didn't work, even though the moth has thrived here. Somehow, the rest of the silk production infrastructure, human and natural, didn't come together the way it has in China.

The Russian thistle comes to mind. It was introduced here long ago, as a forage crop. Somehow, its growth habit in the US led to its popular name, the Tumbleweed. In Eurasia, it doesn't tumble. Nobody knows why.

Back to moths. It's always a pleasure to learn something new and surprising. Having a closeup look at either of these hand-size moths would be a pleasure even greater.