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July 1999
I was sitting outside one sunny afternoon when a yellow and black apparition glided from the trees out back toward the lilac hedge. The butterfly took a detour and circled me closely, a brief acknowledgement. It lighted on a clematis leaf in full sun.
I observed its outstretched wings. It was yellow with black striped markings and its wingspan was about four and half inches. I discovered this was an Eastern Tiger Swallowtail floating around my yard.
This year is the first we've had these butterflies. I suspect it is because of the maturing landscape and the way we manage the yard. The habitat of the Eastern Tiger Swallowtail is mixed or deciduous forests with open areas. This includes forest edges, river valleys and streamsides, roadsides, parks and towns. It even lives in urban areas with the right ingredients, including host plants for the caterpillars and nectar plants for the adults.
The adult Eastern Tiger Swallowtail lays its eggs, singly, on the leaves of host plants. For this species host plants include wild cherry, basswood, birch, ash, willow, mountain ash, lilac and tulip trees. When an egg hatches into a caterpillar, it is already located on the foliage it requires.
These caterpillars have adaptations for surviving in a world of hungry predators, such as birds. Early in life as caterpillars, they closely resemble bird droppings, evidently an unappetizing appearance. They have two false eyespots, quite large, that deceive a potential predator about their actual size. They are solitary feeders. Each weaves a silken mat on a leaf, curling it into a shelter, where the caterpillar rests safely when not eating leaves.
The caterpillar, after growing, molting its skin several times, and eating lots of leaves, finds a protected spot, a permanent location, on which to begin the butterfly's resting stage, the pupa or chrysalis. You won't find a chrysalis on the stalk of an annual plant, because those don't remain upright through the winter. With a silken pad, the caterpillar of an Eastern Tiger Swallowtail attaches its foot to a branch or to bark. Around its middle it also weaves a silken girdle, which helps to secure the chrysalis in its outward leaning angle. While most chrysalises hatch the following spring, some hatch the second spring. This seems to be a way to ensure that drought or other disaster doesn't destroy a total population.
This species of butterfly overwinters in chrysalis form. In Maine, the adult emerges from its chrysalis about the middle of May, depending on temperatures, and seeks sources of nectar. The emergence of these swallowtails coincides with the blooming of lilacs, a favorite of theirs. They are attracted to deeper tubular flowers such as bee balm, phlox, tiger lily, milkweed, clover, dandelion and mint. I saw one nectaring on dame's rocket, a native of Europe that escaped colonial gardens. Also, they are attracted to puddles, wet soil and ponds, where sometimes they can be seen in great numbers. They are on the wing for perhaps a month during which they feed on nectar, court and mate, and deposit their eggs to start the cycle again.
There is a level of life occurring around us that is quiet and diminutive. A parallel response is required if we wish to observe or participate. We must be quiet inside ourselves. Our eyes must see the tiny movements, the slight changes of light and wind, and the incremental development of plants that are easily missed when our attention is monopolized by apparently larger phenomena. In these efforts, we are rewarded twice. We attain a sense of calmness and of being connected with nature, things often obscured by the work-a-day bustle. We experience the wonder of sharing this life with beings that combine fragility with vitality.
By Nancy Coverstone (ncstone@umext.maine.edu), University of Maine Extension Educator in Androscoggin and Sagadahoc Counties
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