August 19, 2012

Interest in moths taking flight

Earlier this summer, a friend asked me about the huge insects covering his apple tree. He described them as hovering like hummingbirds but looking like giant bumblebees.

The insects in question were hummingbird clearwing moths (Hemaris thysbe). They belong to an interesting group called sphinx moths that emerge as large adults for a short period of time, usually between June and early August. 

They are designed for rapid, powerful flight and will startle you the way a passing hummingbird can. They are able to hover, even move laterally, to insert a long proboscis into a deep nectar-bearing flower. Some or all of the scales that typically cover moth wings are absent, making just the network of veins visible, hence the name clearwings.

Many sphinx moths fly at dusk or just after dark but the hummingbird clearwings fly during the day to feed. They are particularly attracted to the monarda in my garden. Anna Botsford Comstock, in her “Handbook of Nature Study,” commented that strongly perfumed petunias are also very attractive to them.

Like other moths, the hummingbird clearwings have a life cycle that begins with eggs that become caterpillars, then pupa, then adults. The caterpillars are known for the long “horn” on the posterior end. They like viburnum and honeysuckle hosts but also eat fruit trees.

The caterpillars eat their way through a few stages and then pupate in shallow soil or leaf litter. If you like to see these moths, try leaving the leaf litter near your home or camp undisturbed for a few seasons. You can attract the adults when they emerge in summer by planting species that have deep nectar-bearing flowers.

These moths and the others in the family Sphingidae have beautiful and intricate patterns. They have widely varying colors, including some that can be completely camouflaged against pine, ash or other bark.

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