Saturday, July 3, 2010

Snowberry Clearwing: The Hummingbird Moth

As the flowers in our gardens burst into their summer display, the critters that crave nectar descend upon them, each intent on sipping its share. From birds to bees, they are all there, and if you aren’t careful, you can mistake one for another. Take for example, the clearwing moths, which for us are most likely the hummingbird clearwing (Hemaris thysbe) or the snowberry clearwing (H. diffinis).

These noisy insects look like a cross between a hummingbird and a bumblebee. Like a hummer, they hover before each flower (bumble bees land) as they uncurl their long proboscises (think tongues) to probes the flower’s nectaries for food. Like a bumble bee, these moths are furry: the snowberry clearwing has black and yellow bands, while the hummingbird clearwing tends more towards dark red and black. All three animals (bird, bee, and moth) have wings that hum and buzz while the animals are in flight. It’s enough to give a gardener pause.

I found the snowberry clearwing pictured above this spring as it supped at the tubular flowers of a native honeysuckle. Honeysuckles are one of the favored plants of both the adults and the larvae. Other plants where you might find the adults hovering include orange hawkweed, thistles, and lilacs. I often see them flitting in and out of my patches of bee balm, along with the hummingbirds.

In the spring adult clearwings emerge from the ground where they have spent the winter sleeping snugly in silken cocoons spun the previous fall beneath the leaf litter. Upon emergence, the “fresh” moths have solidly-colored wings: nearly black in appearance. Their first flight, however, with wings flapping to beat the band, causes most of the scales to fall off, especially near the center of each wing. The end result is wings that are nearly scale-less and therefore look clear.

The first flights begin, and soon the female is sending out a pheromone from a gland located near the tip of her abdomen to signal to any available male that she is ready to mate. Once the deed is accomplished, she lays her newly fertilized pale green eggs singly beneath the leaves of a host plant.

Host plants are those that are favored food items of caterpillars. In the case of the snowberry clearwing, several plants will do. Many are in the honeysuckle family, including snowberry (hence the name), but others include cherry, plum, dogbane and the viburnums.

Summer rolls along and the eggs hatch. Miniscule green caterpillars begin to eat, growing a little more each day. They go through five instars, or growth spurts. As it grows, the larva’s patterns begin to emerge: pale green color with black spots along the sides. These spots are called spiracular circles, for they form around the spiracles, or breathing holes (insects do not have lungs and noses like us for breathing – they breathe through holes in their sides). Additionally, the caterpillar sports a spike, or horn, on its rear end. When it reaches its final instar, this spike is blue-black over most of its length, with white and yellow at its base. Some larvae, however, opt for a more subtle coloration and are various shades of brown. Still, the spiked tail and spiracular circles are good clues for ID.

When the final instar is reached, and the larva has eaten its fill, it drops to the ground, crawls under some leaves and spins a silken cocoon in which it will spend the winter. If nothing squashes or eats it, come spring a new adult will emerge and the cycle will begin again.

Another of the common names for these insects is sphinx moth. This name came about from the habit the caterpillars have of rearing up (and looking sphinx-like) when threatened.

Clearwing moths are insects that almost anyone with a flower garden should encounter, for not only are they fairly common, but they are denizens of open areas, like streamsides, fields, and the ‘burbs. Therefore, it should be fairly easy to find one or more. Here’s my suggestion: the next sunny day, grab a lawn chair (or your Adirondack chair) and kick back in front of your flowers. Have a cool drink handy, and a wide-brimmed hat. Keep your eyes open – you just never know what will fly by.

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Ellen Rathbone

Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.



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