Cool Critters: Tigers swarm Spokane
It’s hard not to be dazzled by the bright yellow butterflies fluttering around the Inland Northwest these days. Not only are they striking in color, but they’re among the biggest butterfly species in the United States.
Tiger swallowtails are so large and showy that they tend to upstage the flowers they pollinate and the plaza water fountains they flit around. Roughly half the size of a human hand, their lemon-yellow wings display black tiger-like stripes and wide black borders. The butterfly’s name comes from both the tiger pattern and the protrusions on their wings that resemble tails of bird swallows.
Two tiger swallowtail species are common in our region, according to Washington State University entomologist David J. James, and author of the book “The Lives of Butterflies: A Natural History of our Planet’s Butterfly Life,” published in 2024.
The two-tailed tiger swallowtail and western swallowtail “are very similar except for the two-tailed tiger swallow tail has two tails on each hindwing,” James explained, while the western swallowtail has a single protrusion on each hindwing. While both species are big, the two-tailed has a larger wingspan reaching 5 inches, he added.
Unlike the famous orange and black monarch, swallowtails don’t migrate. They’re homebodies, typically traveling within a 5-mile radius to feed on nectar, find mates, reproduce and lay eggs on the leaves of certain deciduous trees.
And it’s those trees that make urban areas so appealing to them. With many of the swallowtails’ host trees located in our region’s towns and cities, it’s no wonder we see them so regularly.
“The two-tailed does well in eastern Washington towns because of the presence of green ash trees,” James said. Meanwhile, the western tiger does well due to the abundance of maple trees, aspen, willows and cottonwoods, he explained.
Another cool thing. Tiger swallowtails are master illusionists. On the lower inner margin of each hindwing is a blue and orange “eyespot,” used to thwart off attacking birds and other predators by confusing or scaring them away.
Beauty is fleeting, so enjoy these colorful-winged giants while they’re still around. With a lifespan measured only in weeks, the adult tiger swallowtails will be around until mid-July or so, James said.
Happily for us, they’ll leave behind caterpillars that grow on the broad leaves where they hatch, eventually turning emerald green and developing two yellow and black eyespots. When confronted by intruders, they’ll extend an orange forked tongue-like structure. Dolled up in scary mimicry, the caterpillar resembles a stout, green viper snake with giant eyes. Its message to predators: Don’t mess with the tiger.
Come this fall, the caterpillars will have formed a chrysalis – a hard shell that envelopes the insect until it morphs into a tiger swallowtail butterfly next summer. However briefly, we get to enjoy our resident butterflies all over again.