Into the Woods with Curio: Giant Silk Moths
Doug Smith
“Thus says the Lord who made the earth,the Lord who formed it to establish it—the Lord is his name: Call to me and I will answer you, and will tell you great and hidden things that you have not known”
Jeremiah 33:2-3
If you are at Beacon this June or in early July keep a look out for an amazing insect – a giant silk moth! It might be a light green Luna moth, with a pair of twisted ‘tails’ on the bottom wings, or one of the several species with reddish-brown colouring, or possibly a pale-yellow Io moth. There are potentially 9 species of giant silk moths found in Ontario, though only 6 of these are commonly seen in Muskoka. Besides the Luna and Io there are also the cecropia, Columbia, polyphemus and promethia moths. Depending on the species and whether it is a male or a larger female, (she can have up to 100 or more eggs inside her body) any of these moths are as thick as a man’s thumb. Their wingspan is twice as large as that of a monarch butterfly -- as large as that of a hummingbird.
It used to be that these beautiful moths could be found under the outdoor lights of any of the camp buildings. The old incandescent lighting attracted them each night, along with many other flying insects. About 10 years ago Beacon replaced this lighting with low voltage LED lighting. This low-impact lighting is less attractive to moths and other flying insects and causes much less light pollution. Another important measure that camp has put in place is a good steward of God’s Creation.
Why are these moths at the lights? CBC’s Quirks and Quarks host Bob MacDonald mentions this; “A new study suggests that insects flit around artificial light at night because they are confused, not because of a fatal attraction. Sam Fabian and Yash Sondhi used motion capture and high-speed imagery to understand insects’ flight patterns and found that they always turned their backs to the light, which left them trapped in a spiral around the source. This suggests the insects are mistaking the lights for the sky, which normally helps tell them which way is up. The research was published in the journal Nature Communications.”
Some scientists also believe this behaviour is why there are far fewer flying insects than there used to be. Too many are dying, and being predated, when trapped at artificial light sources, especially lights that are not environmentally friendly.
Fortunately, there are still giant silk moths in Muskoka and at Beacon.
Despite their surprising size, these are harmless insects. They have no pincers or stingers, or even mouths. That’s right, no mouths because they don’t eat. They ate as caterpillars, and now that they are adults, they just need to find a mate. They use chemicals to help locate each other. The female releases pheromones that attract the males – 1 drop can be detected by the male, using his amazing antenna, up to one kilometre away. Once they have mated the females lay their eggs, and then die. These moths only live a week or two as adults.
The eggs hatch within 1 to 2 weeks, and the tiny, (at first) caterpillars start eating right away on the leaves of their host plant – cherry or birch or sumac, oak or poplar. Within 2 months – by late August or early September – they will be up to 10 cm or more long. That is a large caterpillar. Then they find a place to pupate and spin their cocoon, which takes about a day, and over 1 kilometre of silk thread. This seals them into their leafy enclosure for the winter, to emerge next June as moths and start the cycle again.
Another amazing example of the incredible variety of God’s Creation which he shows us in His love for us.