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Story By Harvey Thommasen with Photography Jay Cossey
One of the hatches I look for in the spring has nothing to do with rising trout. But sighting the Milbert’s Tortoise Shell butterfly (below) can add as much to a fisherman’s day as any prolific insect emergence. The scientific name for this butterfly is Nyphalis milberti - but its common name is far more descriptive. It is known as the Fire-rim Tortoise Shell, and is said to be the most common and colorful of the Tortoiseshell butterflies found in Canada. And beautiful it is! Once seen, it is hard to forget. It is a smallish butterfly (wingspan of 1.75 –2"). The entire inner area on the upper side of all four wings is dark brown to black, edged with brilliant gold. The outer wing margins are a uniform black, broken only along the leading edge of the forewings. Within this black outer wing margin are rows of crescent-shaped blue spots. The flame-like upper surface of this butterfly is said to is unique, no other butterfly seen in the coastal valleys of the Pacivinc Northwest has this color combination.
Like the Anglewing and Mourning Cloak, when the Tortoise Shell butterfly settles on a gravel path, the mottled gray undersurface renders it almost invisible to would-be predators. Also look for the Sara’s Orange Tip butterfly. This butterfly seems to really enjoy the feel of sunshine on its wings. More often than not, after landing on gravel, the Sara’s Orange Tip will quickly face the sun and then spread its wings to expose its striking, rounded, orange patches located on the tips of its front wings. Presumably, the butterfly is attempting to absorb as many sun rays as possible, in an attempt to raise body temperature, thereby enabling it to fly faster if the need arises. If you approach too closely this butterfly will close up its wings, hiding the orange wingtips and exposing the marbled green and white wing undersurface. Reach down to touch one and it will flash its orange spot and then fly rapidly down along the woodland trail. Spring is mating season for all of the butterflies. The male butterflies are busily flying about, patrolling back and forth, looking and sniffing for females to mate with. If patrolling proves unproductive, many of the males will conserve energy by simply perching on favorite branches and waiting for females to fly past. Anglewing, Mourning Cloak, and the Milbert’s Tortoise Shell butterflies are all said to predictably perch – usually on a rocky place just below a hilltop, from about 11 am or 12:30 pm to 5 pm every day during mating season. After mating takes place females fly around looking for good spots to lay their eggs. As a general rule, eggs will be laid on plants, which will furnish the caterpillar with its favoured food. If the female makes a mistake and lays her eggs on the wrong host plant, the caterpillars will starve to death. The female Mourning Cloak butterfly (below right) will lay her tan white eggs in a cluster (up to 250), in rings circling a host twig near its tip, rarely on leaves. Caterpillars emerge from the eggs in one to two weeks and begin feeding right away. The full grown Mourning Cloak caterpillar grows to be 2 3/8" (60cm) in length, is blue-black, has a row of red spots on its back, many minute white dots on its back and sides, branching spines, a black head, and five pairs of fleshy orange-red prolegs. Large numbers can sometimes be found feeding together, sometimes even defoliating trees and shrubs. Favourite tree foods include Willow, (Salix spp), Black Cottonwood (Populus trichocarpa), Trembling Aspen (Populus tremuloides), Paper Birch (Betula papyrifera), Mountain Ash (Sorbus spp). Favourite shrubs include Hardhack (spiraea) thimbleberry and Salmonberry (Fubus sp), as well as Wild Roses (Fosa spp). When fully grown the caterpillars leave their food plant and individually find protected spots in which to pupate. Pupation lasts about two weeks and then the insect emerges as an adult.
Young caterpillars may eat leaves, but the older ones seem to prefer to eat the flowers and weed pods. Favourite mustard plants include Tumbling Mustard (Sisymbriium officinale), Sickle-pod Rock Cress (Arabis sparrsiflora), Wintercress (Barbarea vulgaris), Tansy Mustard (Descurainia pinnata), and Fringe-pod (Thysanocarpuc curvipes). The female Fire-rim Tortoise Shell lays her pale green eggs in a cluster of several hundred, on the underside of a stinging nettle (Urtica spp) leaf. The young larvae hatch from the eggs within five days and initially remain together as a small colony. Shortly after emergence, these caterpillars enclose themselves collectively in a silken web atop the stinging nettle plant, within which they feed and mature. When fully grown the spiny, black (Upper half + dorsal side) and green (Under side + ventral side) caterpillars measure about 2.5 cm long. The older larvae tend to be solitary, living within a leaf that is rolled (usually upward) and tied above the larvae with silk. Pupation lasts about three weeks, and then emerges the fully developed butterfly. New generation adults can be seen any time after late June through to September. These butterflies have the interesting habit of migrating up to alpine mountain meadows to sip nectar from the wild flowers found there. They feed on alpine flowers in July to August, and apparently, return to the lower mountain in September to hibernate. The female Comma Tortoise Shell butterfly lays her eggs in small clusters on the host plants, namely Birch, Willow, Alders, and Cottonwood. The caterpillars, which emerge from these eggs, grow to be greenish coloured, with a variety of white speckles and stripes. The body and head are sparsely covered with black bristly spines. The gregarious larvae feed on leaves of Paper Birch (Betula papyfera), Trembling Aspen (Populus tremuloides), and Willow (Salix spp). When fully grown the caterpillars pupate, and adults emerge anytime after mid-July. Adults are in flight until about early September. The adults can be seen feeding on sap, fruit, mud, and occasionally flower nectar (esp. goldenrod flowers). They then go into hiding and hibernate the winter away, waiting to come out again the following April and May. Butterflies may not be of interest to fly fishermen as patterns to be matched, but they add something special and beautiful to the day, when you encounter them along a stream. END NOTE: Harvey Thommasen is a medical doctor who lives and teaches in Prince George, British Columbia. He is a naturalist and fly fisherman. Jay Cossey is a London, Ontario based photographer whose work can be found at: http://www.images.on.ca/JayC/ |
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The female Sara’s Orange Tip attaches her cream colored, spindle-shaped eggs to stems near the top of stalks or to the underside of wild mustard leaves. The caterpillars which emerge from these eggs are green (darker green beneath), with black points and cream lateral strip (edged below by a dark-green line), this extending onto the green head.
