Humming along: The most beautiful moth
Spending time in the garden is always a wonderful way to enjoy nature and very occasionally one may be fortunate enough to spot one of our more dramatic and beautiful moths, the hummingbird moth. Similar in size to their namesake birds they can also be found hovering at flowers when feeding on the nectar with their extended proboscis. Unlike most moths, their wings are quite narrow and they are some of the fastest flying insects around. While the majority of moths fly about during the nighttime, hummingbird moths are daytime fliers. Also like hummingbirds, they beat their wings very rapidly which adds to the likelihood of mistaking them for the birds they are so aptly named after.
Hummingbird moths are in the Sphingidae family of moths which includes various species of sphinx and hawk moths. These very large moth species are always a treat to encounter, unless of course you’re not a fan of moths.
The caterpillars of hummingbird moths are also very large and finding one in the garden can be startling. Typically, the caterpillars are a bright green, thick-bodied and a few inches in size; about the size of an adult’s finger. Smooth with only a few scattered hairs, they can be further distinguished by what’s referred to as a horn at the top end of their body, resulting in the caterpillars being called hornworms. While this horn can appear dangerous, it is not and is usually softer than it looks. Most often the caterpillars are first noticed when they are looking for a place to pupate in the fall. At that time they typically fall to the ground and crawl to a suitable spot which is usually under leaf litter or just below the surface of the soil. In Canada, there is most often only one generation per year. It is the pupal stage that over-
winters. Adults emerge in the spring, mate and lay eggs that then hatch and feed on plants throughout the summer months.
The caterpillars prefer to feed on plants like honeysuckle, hawthorn, snowberry and plants in the prunus genus which includes many of our fruit trees. While these large hummingbird caterpillars (hornworms) are voracious and can consume a large quantity of plant material, there usually aren’t many of them at any given time. As a result, the use of chemicals to control them isn’t often necessary. And because they are so large, it is quite easy to see them and simply pick them off any plants that are being unduly damaged. Occasionally larger numbers may occur or they may find smaller vegetable or flowering plants that would be quickly devoured if left unchecked. In these cases, the biological insecticide BTK ( Bacillus thuringiensis kurstaki) can be used to successfully control them.
It is important to remember that hummingbird moths are pollinators like many other insects and they will use their long proboscis to drink the nectar from a wide variety of flowers, similar to flowers that hummingbirds would feed from. When feeding on nectar, they will brush against pollen that will become attached to their bodies and be transferred to other plants. So while the large, voracious caterpillars may be a bother, the adults are completely beneficial with the added bonus of being beautiful to look at.
Sharon Moffat has a Plant Science degree and works for the City of Winnipeg's Insect Branch.
Hummingbird moths, so named because they share the ability to hover in the air like hummingbirds.
Hummingbird clearwing moth.
Caterpillars are also known as horn worms, due to their harmless "horn".