Tale of the Swallowtail

Drama in black. That's a four inch wingspan!

A scrap of black stirred on the pavement like a triangular black sail at my feet. An outsized butterfly perched delicately on the cement sidewalk. The spring days have been warm, but the nights are chilly. I lifted the butterfly and placed her safely in the sunlit crotch of a mesquite tree.
She’s a black swallowtail. This butterfly is somewhat common, successful in gardens and along roadsides. She can’t regulate her own body temperature, as she’s cold blooded. On this morning she shivered to keep warm. Temperatures below a certain point cause swallowtails to lose power altogether.
She drifted lifelessly from the mesquite. I scooped her up and cupped her against my fleece vest. At home I put her in a shoebox and placed the box on a sunny bench. Later in the morning I took the box into the garden and lifted the lid, hoping to see her fly away. But the butterfly stayed motionless. Set into a patch of nasturtiums she only moved lethargically to the edge of a blossom. Examining her iridescent wings I could see a tear in one and a little hole in the other. My heart sank.
But then the swallowtail rubbed her face with a long front leg. Her thorax flexed, bending nearly in half. Humbly she lifted into the air and fluttered west with the breeze, floated over the block wall and disappeared.
When black swallowtails emerge from chrysalis in March they uncrumple two damp and puny wings. They pump fluid from their bodies through the veins of each wing, literally plumping them up. When all parts are dry, the brand new butterfly takes off. Cornell University’s Ask a Scientist has this description of butterfly flight: “With any given stroke of its wings a butterfly produces much more lifting force than it needs to stay in the air. Instead of flying smoothly along butterflies tend to lurch up and down and side to side….like leaves tumbling in a strong wind.”
The flight of the butterfly has plenty to keep scientists intrigued. Using strong thorax muscles butterflies slap the air with wings set at a steeper angle than birds, pushing more air in flight. When they hover near a flower, their wings have twice the efficiency of any hovering bird. “Wake capture” is the term for a butterfly’s’ ability re-use swirls of air from previous flight strokes.
This black swallowtail will look for host plants whose chemistry matches hers. She uses tiny hairs on her legs to detect the chemical signals. The hairs are taste receptors activated when she drums her feet on the leaves, releasing the plant’s liquids.
Swallowtails lay eggs on the leaves of dill, fennel, carrots and Queen Anne’s lace. Once the eggs hatch the instars keep eating, growing and shedding their skin until a green caterpillar emerges sporting black bands and white spots. This caterpillar will morph into a chrysalis, completing the miraculous cycle.


3 responses to “Tale of the Swallowtail

  1. Pingback: Big Rains Bring Bugs | onelookout

  2. Lovely, left me with a lump in my throat and well wishes for the lovely lady that visited your yard. And, very informative….the world of insects is filled with abundance of fascinations.

  3. Fascinating post and wonderful photo.

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