Please consider making a tax deductible donation (or becoming an underwriter) to bring our Monarch Butterfly documentary Beauty on the Wing: Life Story of the Monarch Butterfly to American Public Television. To Learn More go here and here: Over the Moon
It’s very easy to see the difference between a male and female Tiger Swallowtail.
The female Tiger Swallowtail’s tail end of her lower wings are more vividly colored, with strongly pronounced cells of orange and a greater degree of iridescent blue.
Female Tiger Swallowtail drinking nectar from Phlox
Male Tiger Swallowtail. Note the very dark border along the tail end of the male TS lower wings, with very little blue iridescent scales
The Eastern Tiger Swallowtail utilizes a large variety of host plants, mostly trees, such as wild black cherry, tulip tree, sweet bay (magnolia), cottonwood, ash, birch, and willow.
Please consider making a tax deductible donation, or becoming an underwriter, to bring our Monarch Butterfly documentary Beauty on the Wing: Life Story of the Monarch Butterfly to American Public Television. To Learn More go here and to DONATE go here. Thank you!
One of our West Gloucester readers, DB, spotted a Giant Swallowtail in her garden! She was too surprised by its appearance to take a photo, and I completely understand why. They are fantastically large in size, as large as a Cecropia Moth. Giant Swallowtails are more of a southern species, but sometimes make it this far north and east, especially during long stretches of hot, humid weather.
Readers, please keep your eyes peeled, and if you can, try to get a snapshot, and please let us know of your sighting. Look for Giant Swallowtails nectaring in your garden; they especially love native Marsh Milkweed, tropicals such as lantana and bougainvilla, also butterfly bushes, Wild Sweet William, and honeysuckle.
I have only see one once in my garden (in 2012) and it was drinking nectar from the lantana growing in pots on my patio. By the time I ran indoors and back to the garden with camera, the Giant Swallowtail was gone. The photos are from wiki commons media so you can id the butterfly if you see one in your garden. Happy spotting!
The yellow will be paler on an older butterfly as the scales wear off, but look for the arrangement of the spots for an id.
Giant Swallowtail Butterflies, with a wingspan of up to 6.5 inches across, are noticeably larger than Eastern and Canadian Tiger Swallowtails (Eastern Tiger Swallowtail, left, Giant Swallowtail, right).
I have received many emails in the past several weeks from people wondering what is the large, yellow butterfly that they are seeing perusing their gardens and neighborhoods. I imagine they are observing a tiger swallowtail–either an Eastern Tiger Swallowtail or a Canadian Tiger Swallowtail. They may not recognize it as either species because tiger swallowtails are highly palatable. Their delicate tails, and then some, may have been sheered away by hungry birds snipping. The first two photos below show a newly emerged tiger swallowtail with tails intact and a swallowtail without tails.
I wrote the following column several winters ago after having recently read A Tale of Two Cities. If you can bear to read about winter storms during this delicious stretch of warm weather, you will find information that will be helpful in identifying whether visiting your garden is a Canadian Tiger or an Eastern Tiger Swallowtail. Additional identifying photos are at the end of the column.
A Tale of Two Tigers
Recalled to Life
As seed and plant catalogues pile ever higher in my ever-shrinking office, I am culling all for sources of delicious vegetables and herbs, native plants, fragrant cultivars, and plants that will expand the Lepidoptera and songbird habitat. With inviting descriptions accompanied by enticing photographs, it is difficult to exercise restraint. Absorbed in thoughts of new life in spring, I am reminded of an incident that occurred at about this same time last year.
My husband and I had returned home from a venture along the backshore to witness the waves cresting in the aftermath of a late-winter storm. With great gusts blowing up from the south, the storm was tropical in temperature, but not in degree of ferocity. Drenched to bare skin, we came in through the cellar to remove our soaked clothing, where, to our dismay, we encountered a newly emerged tiger swallowtail butterfly, unable to fly, with its wings dragging along the cold stone cellar floor. I carefully picked it up by holding the butterfly along the sturdy leading wing margin, and brought it into the warm kitchen. Its wings had not fully unfurled and the butterfly was in distress. We provided a twig for it to crawl upon, which would have allowed its wings to hang down, and then, perhaps, fully expand. That was unsuccessful and the butterfly preferred instead to simply rest in my hands. We offered it a Q-tip soaked in sugar water and I cupped my hands and held it there for a long time, hoping the warmth would recall it to life.
Within the brief moment of time a butterfly emerges, if just one of the steps in the complicated dance goes awry, the creature will likely fail. The crimpled, wet wings are tightly compacted within the chrysalis. The butterfly pushes head first through the pupa case and upon emerging, with its crochet hook-like feet (tarsi) grasps at nearby surfaces. Body fluids are drained from the swollen abdomen and pumped through tubular wing veins (called struts) to the very outer margins of the wings. The butterfly’s double drinking straw (proboscis) must zip together, or it will be unable to nectar. For several hours after eclosing, it remains in a stationary state, the most vulnerable of positions, to allow its wet wings to dry thoroughly. The mystery of how the tiger swallowtail came to be in our basement, and why it eclosed in early March, prompted me to learn more about this magnificent species of butterfly.
The Golden Thread
Tiger swallowtails are recognized by their four rows of tiger-like yellow and black stripes and thin black tails extending from each lower wing. Canadian Tiger swallowtails are found in all provinces and territories of Canada, northern New England, and eastern New York. Eastern Tiger Swallowtails are more common from southern New England and south to Florida. We are fortunate in Massachusetts to be located where overlapping of both species occurs. Canadian and Eastern Tiger Swallowtails are closely related and were not recognized as separate species until 1991. The clearest way to see the difference is to compare wingspan. The Canadian is smaller, with a wingspan of just under 3 inches; the wingspan of the average Eastern is 4.5 to almost 5 inches— the southern female ranks as the largest butterfly of the East Coast. Canadian Tiger Swallowtails are generally a paler yellow and the darker border next to the body is thicker. When the wings are folded, the yellow sub-marginal band on the fore wings is largely continuous, not interrupted by black wing veins. Tiger swallowtails are highly palatable and, as a defense against predators, have evolved with rapid wing movements and erratic flight patterns, which make these differences between the two species difficult to discern without side-by-side specimens or photos.
Species: glaucus ~ Eastern Tiger Swallowtail
Species: canadensis ~ Canadian Tiger Swallowtail
The purpose of identifying the different species is relevant when planting to encourage tiger swallowtails caterpillars to colonize your garden. Host trees for Canadian Tiger Swallowtail caterpillars include native species of birch (Betula), black cherry (Prunus), and aspen (Populus). The Eastern Tiger Swallowtail caterpillars have adapted to a wide range of host trees from multiple families, especially wild cherries (Prunus sp., Prunus virginiana), tuliptree (Liriodendron tulipfera), ash (Fraxinus), and sweetbay magnolia (Magnolia virginiana) in the Deep South. Both species are generalist when nectaring. I most often observe tiger swallowtails nectaring at plants with clusters and panicles of small florets, for example, native buttonbush (Cephalanthus occidentalis), Joe-pye weed (Eupatorium purpureum), common milkweed (Asclepias syriaca), butterfly bush (Buddleia davidii), and Verbena bonariensis.
Adding to the challenge to accurately identify whether Canadian or Eastern, female Eastern Tiger Swallowtails may exhibit sexual dichromatism, a dark-phase that mimics the highly unpalatable and toxic blue/black coloration of the Pipevine Swallowtail. The yellow form of the females is more typically seen in our region and is similar to the males, except that the hindwings above the black margin are covered in beautiful blue iridescent scales. Iridescence in wing scales is an example of how Lepidoptera have evolved with structural color that is disorienting to predators. The flashes of light created by the iridescent scales, combined with undulating wing beats caught in sunlight, causes hungry birds to be confused. The characteristic “tails” that lend swallowtails their common name are significant aerodynamically. Airflow is directed over the wings, enabling extended glides at higher angles, whereas Lepidoptera with more broadly cut wings would normally stall.
We look for tiger swallowtails eggs on the topside of host tree leaves. The spherical, green, pinhead-sized singular eggs are not easy to see amongst the surrounding foliage. The first instars are dark brown with white markings, which resemble bird droppings (another defense against birds). Later stages become luminous light green, with yellow and black thoracic “eyespots” that mimic the eyes of small snakes. Tiger swallowtail caterpillars have yet another defense against predators. When threatened, they will evert their osmeterium (a unique horn-like appendage that resembles a snake’s forked tongue), which emits a smelly secretion.
Most tiger swallowtail caterpillars feed at night, spending the day in a rolled-up leaf mat bound with spun silk. When ready to pupate, the caterpillar turns chocolate-brown and spins a silk girdle, a “thread of life” that supports it in an upright position as it begins to pupate. The chrysalis resembles a twig, or knob of wood jutting from the trunk, and the thread holding it in place is as fine as a strand of golden thread. In the case of the chrysalis formed in late summer, the pupa enters a state of diapause and the adult emerges in spring. The same thread of life girdling chrysalis to branch will keep the pupa secure through winter snow, sleet, and ice, and during violent spring thunderstorms and nor’easters.
The Track of the Storm
Artfully mimicking the twiggy growth and withered leaves of the lantana (Lantana camara)standards we winter-over, it became clear how a tiger swallowtail chrysalis could find its way into our cellar. Prior to bringing plants indoors, we now thoroughly examine all for signs of Lepidoptera pupa. The unsolved mystery is why. The eerie atmosphere created by the tropical storm in winter, coupled with the unsettling early emergence of the butterfly is haunting still. Perhaps the electric energy and unusual balmy temperature carried by the storm caused the butterfly to eclose several months too early. Whatever the reason, I return to the not unpleasant task at hand—catalogues beckoning with plants to enhance the songbird and Lepidoptera landscape—anon to be engaged in the garden of possibilities.
It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all going direct the other way . . . ~ A Tale of Two Cities by Charles Dickens