Fooled again! While I was in my garden the other day, in the distance I saw a flash of wings and a tiny body bobbing in and out among the flowers. I was looking forward to seeing a Ruby-throated Hummingbird (Archilochus colubris). On closer inspection, I realized I had spotted instead a Hummingbird Clearwing Moth (Hemaris thysbe).
This member of the hawk moth family (Sphingidae) is one of four clearwing moth species in North America. Two are most common: the Hummingbird Clearwing and the Snowberry Clearwing (Hemaris diffinis). Although both are found throughout North America, the Hummingbird Clearwing is abundant in the east and the Snowberry Clearwing is more often seen in the west. Hummingbird Clearwings are easily identified by their fuzzy burgundy and green backs. The Snowberry Clearwing’s back is yellow and black. And you can tell the difference between these moths and the Ruby-throated Hummingbird by their size. At an inch-and-a-half (4–5.5 centimeters) long these clearwings are half as big as a hummingbird.
July is a perfect time to catch a glimpse of this day-flying moth collecting nectar. If you have flowers with long corolla tubes—such as Meadow Phlox (Phlox paniculata), bee balms (Monarda spp.) like our native Wild Bergamot (Monarda fistulosa), and verbenas—there is a good chance you will see one feeding. These moths extend their long, straw-like proboscis in and out of flowers while beating their wings at more than 70 times per second—so fast they look almost motionless in the air!
Here in Connecticut and farther north, the Hummingbird Clearwing’s life cycle has one generation. Females lay small green, circular eggs on the underside of the leaves of their host plants. These include viburnums, such as native Arrowwood (Viburnum dentatum), hawthornes (Crataegus spp.), honeysuckles (Lonicera spp.), snowberries (Symphoricarpus spp.), and cherries and plums (Prunus spp.). A week later, a green caterpillar with a spur on its hind end hatches to feed on these host plants. After about four weeks and several growth stages (called instars), the fully grown caterpillar burrows into the soil and metamorphoses into a hard-shelled, brown pupa that will overwinter in your garden.
So instead of raking your leaves and leaving them at the curb in the fall, consider using them as mulch under your trees and shrubs. You will not only be providing a place for these moths to overwinter, but feeding your trees and shrubs too.