Prairie Ridge Ecostation

Eastern Tiger Swallowtail

Papilio glaucus

Over the last few weeks we've begun to see more insects active at Prairie Ridge.  One of the showiest and largest insects we see is the Eastern Tiger Swallowtail.

Eastern tiger swallowtail

Eastern Tiger Swallowtails are large butterflies in the swallowtail family, Papilionidae.  Like other swallowtails, they have long tails protruding off the back of the hind wings.  Eastern Tiger Swallowtail males are yellow with black stripes and black bands around the wing edges, but the females come in two different forms.  The typical female looks very similar to the male, but with blue spots on the upper surface of the hind wings.  In the dark morph, the wing sections that are normally yellow are replaced with dark gray or black so that the majority of the butterfly is dark except for the small yellow, orange, and blue markings on the outer edges of the wings.

In the south, Eastern Tiger Swallowtails have three broods, so you can see larvae and adults throughout the spring, summer, and into early fall.  Adult males patrol, flying around looking for females who are receptive to mating.  After a pair couples, the female will lay her eggs one at a time on leaves of several different trees, including cherry, Sweetbay, Tulip Tree, birch, and willow.  The caterpillars that hatch from the eggs eat the leaves, molting and growing.  For the first three instars (growth stages in the caterpillar), the caterpillars are bird dropping mimics, a great defense against predation.  When they molt into the fourth instar, however, they become green with two black, yellow, and blue eyespots on the thorax near the head.  The caterpillars will turn brown just before they pupate and transform into adults.

Throughout their season, the Eastern Tiger Swallowtails will feed on a variety of different nectar sources, including cherry, milkweeds, and Button Bush.  However, you will occasionally find adults feeding from other sources.  You may come across large groups of males or single females "puddling," using the proboscis to suck moisture from puddles on the ground.  Puddling helps the butterflies gather important salts and proteins that they can't get from their otherwise sugar-rich nectar diet.  Likewise, you will occasionally see adult Eastern Tiger Swallowtails feeding on dung, carrion, or urine as these food sources provide essential nutrients lacking in their primary diet.

On your next visit to Prairie Ridge, take a walk along the Forest Trail and head down toward the creek.  If it's a nice day, you are sure to see many Eastern Tiger Swallowtails flitting around along the edges of the trees, looking for flowers and mates.  You may also catch a glimpse of the Red-spotted Purple or Zebra Swallowtail butterflies, so why not stop by and go for a butterfly walk?  We've got many spectacular butterfly species, so you're likely to see something amazing!

Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive.