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Tuesday, October 4, 2011

A “Giant” Backyard Discovery

It was a day just like any other. Except that when Abby Colihan glanced out the window of her home into her garden, she noticed something different. It looked like a very large pile of bird guano, but upon closer inspection, Abby discovered it to be a caterpillar like none she had ever seen before.

The caterpillar was that of a Giant Swallowtail, a species that before July 30, 2010 had never before been seen in Vermont! This distinctive butterfly is similar in size to our Tiger Swallowtail butterfly with a striking mixture of black and yellow, with dashes of blue and red. Larvae feed on plants in the citrus family (Rutaceae) and resemble bird droppings from above (see picture above). Get up close to one, and it will try to fool you into thinking it is a snake (see picture below). If you still dare mess with this caterpillar, it will reveal its large antennae-like osmeterium that can give off harsh-smelling chemicals.

For some time it was suspected that Giant Swallowtail may arrive in Vermont. This species is known to move north some summers, establishing itself where it finds suitable food plants. In 2008, butterfly expert Bryan Pfeiffer noted that the Giant Swallowtail had been seen near Lake George in late August... it was already on its way. This Montpelier record constitutes only the second documentation of larvae in Vermont, and the farthest north this species has been documented in the state. So why didn’t anybody see this Giant Swallowtail before it laid eggs in Abby’s garden as it flew down the streets of Montpelier? And how did Abby know these caterpillars were special?

Stay tuned to our next blog update to learn how you too can discover a rare creature in your own backyard.

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