Wildlife Watching Wednesday: The Regal Giant Swallowtail
By: Tom Berg
Butterflies are always fun to watch as they fly around our gardens, flitting from flower to flower as they sip nectar and pollinate the plants. Some of the largest and most interesting butterflies around here are swallowtails. Although Tiger Swallowtails, Zebra Swallowtails and others are big and beautiful, they are not as large and majestic as the king of the swallowtail world: the Giant Swallowtail.
Although they are considered common throughout their range (especially along the east coast), giant swallowtails don’t seem to be particularly common in my home state of Indiana. However, when they show up in your yard or garden they are easy to notice. These swallowtails are the largest butterflies in North America, sometimes having a wingspan measuring almost 7.5 inches wide!
Giant swallowtail wings are dark brown (almost black) when viewed from above, with a large horizontal yellow line across the forewings. The hind wings each have a diagonal yellow line made up of yellow spots. The undersides of the wings are mostly yellow. They use their large wings to glide and float between wing beats, looking very unhurried as they flit and fly along. These swallowtails drink nectar from flowers like phlox, azalea, milkweed, goldenrod, honeysuckle and many others.
In their larval stage, giant swallowtail caterpillars are preyed upon by ants, wasps, spiders and certain flies. Their defense against these insect predators is pretty amazing – they have a bright red Y-shaped gland that rears up from behind their head which resembles a snake’s forked tongue. This defensive gland has a noxious smell and is covered with a toxic mixture of different acids. If the enemy doesn’t leave because of the smell, the caterpillar attempts to wipe the acids onto them. That’s usually enough to cause a retreat from almost any attacker!
Giant swallowtail caterpillars have a different defense against birds, which are their largest enemy. Birds love to pick off caterpillars from leaves and tree branches as they move through the forest. In their early stages, these swallowtail caterpillars hide from view by resembling bird droppings. They are sometimes even called bird poop caterpillars!
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