ADVENTURES of a backyard naturalist
Last weekend, I spotted several swallowtail butterflies flitting around the back garden — to say I was thrilled to see them would be an understatement — butterflies add an extra dimension of beauty and joy to a flower border. They are the very essence of summer. After spotting the visitors, I grabbed my camera and tried to capture their arrival, but I couldn’t keep up with their lively flight patterns — this was not a leisurely visit.
The eastern tiger swallowtail, a large yellow and black butterfly, took a quick tour of the garden and then disappeared. I suspect she was looking for black cherry, cottonwood, willow, tulip tree, ash or birch, her preferred host plants, or maybe she was just looking for nectar plants like honeysuckle, milkweed, thistles or other urban flowers. In any case, she dropped by, but did not stay long. (Note to self: maybe I should plant one or more of the above plants to encourage longer visits.)
The eastern black swallowtail, on the other hand, was definitely on a mission. She darted around the circle garden several times, pausing briefly on the fernlike leaves of the dill — she moved so quickly that I could not capture her stops with my camera.
When the swallowtails stop by for a sip of nectar midsummer, they visit the zinnias, Brazilian verbena and coneflowers at a leisurely pace, and I have plenty of time to capture their beautiful wings. But this visit was very different and I was determined to see what she was up to. I made a mental note of a few of stops that she made — I wanted to see if she was depositing eggs in the dill.
Last night, armed with a small photo lupe with a 5.5x magnification (the kind of lens we would use to examine slides, back in the day), I tried to retrace the flight of swallowtail, looking for caterpillars or eggs on the dill. They were surprisingly easy to find — within a couple of minutes I discovered three tiny black specks (the larvae) and two tiny bubbles (the eggs). The photo lupe came in very handy to actually ID the specimens, they could easily be mistaken for specs of dust when viewed with the naked eye.
I pulled out my camera gear and headed back into the dill patch armed with a 200-mm macro lens to capture a little magic.
Magnified, the tiny yellowish bubbles resemble exquisite pearls. The female butterfly deposits the eggs singly on the tiny stem of young members of the carrot family: dill, Queen Anne’s lace, wild parsnip and sweet fennel along with parsley, rue and celery.
The miniature eggs are remarkable, with magnifying lens you can actually see the developing caterpillar through the translucent egg. I’ve never seen anything quite so amazing.
Within a few days (four to nine is typical) the eggs mature to the larval stage (10 to 30 days) and finally to the pupal stage (nine to18 days) before emerging as butterflies. In southern Ontario, there are typically two generations in a season, the second generation may overwinter as pupae.
The tiny black specs I found on the dill were actually miniature caterpillars, called second instar larvae. Magnified with a macro lens, the black body ringed with banding and studded with prickly protrusions was clearly visible.
A white saddle marks the centre of larva. Older larvae are green with black transverse bands containing yellow spots. I don’t mind if the caterpillars eat their fill of dill, it was planted to share.
The black swallowtail can be found throughout southern Ontario, Manitoba, Quebec and the Maritimes. They enjoy a variety of habitats including meadows, open fields, roadsides and backyards, making them one of the easiest butterflies to attract to your garden.
A sunny garden with four to six hours of sunlight each day is ideal, offer a diet of milkweed, red clover, purple coneflower along with members of the carrot family such as carrots, dill, fennel, parsley and rue. Avoid the use of pesticides, black swallowtail are very sensitive to these chemicals.
The adult wingspan is seven to 8.4 centimetres. The female is typically larger than the male. The upper surface of the wings is black with two rows of yellow spots. The spots are larger and more prominent in males, and smaller and a lighter shade in females. Powder blue dots appear in the tail above a red eye in the male, the female has more pronounced blue markings above the red eye. The black colouring is a defence mechanism, the colouring mimics the poisonous pipeline swallowtail.
Since that first discovery, I have found more black swallowtail butterfly eggs in a second patch of dill.
If all goes as planned, there should be a young generation of butterflies populating my garden by the end of July — by then, my crop of zinnias, coneflowers and butterfly weed will be ready to welcome them.