Species of the Month, July 2022: Moth Nights in Norfolk
by Mary Gartshore

In the 70s I was travelling north in Nigeria when I met a Polish scientist who counted the numbers and species of moths coming to his porch light every night. Decades later I am still impressed by the amount of data he collected and analyzed. The diversity and abundance of moths makes them ideal for measuring ecosystem function.

There are more than 3200 species of moths in Ontario and a growing following of serious hobbyists discovering new records and species. Juvenile moths – caterpillars – consume huge volumes of plants and fertilize natural areas with tonnes of droppings. Caterpillars are the main source of food for songbirds and their young during summer. Caterpillars of some moths are specific to a single food plant such as the Canadian Owlet that feeds on Tall Meadowrue. Some adult moths such as the giant silk moths like Cecropia do not feed at all as adults. Others are important
pollinators such as sphinx moths. Mournful Thyris feeds on mammalian feces to acquire nitrogen for egg production.

Only a handful of moth species harm human enterprise. A recent species – Western Bean Cutworm Moth – has arrived from Mexico enabled by the continuous landscape of corn-soy. By 2015 its numbers sky-rocketed but have receded due to Bt agents bred into GMO corn varieties. While adult moths are harmless to humans, their caterpillars may have some impressive defenses such as stinging hairs of Monkey Slug. Several have told me that the iconic Luna was instrumental in choosing to become biologists. Most moth species are attracted by mercury vapour or UV lights and the newer LED lights using traps or bed sheets for moths to roost on. Photos posted to iNaturalist can be identified. National Moth Week begins on 23 Jul 22 – let’s celebrate their beauty and diversity.