Comox Valley Naturalists Society
Knowing Nature . . .
June 2, 2006
A few years ago we went on a butterfly walk with some experts. They had flowing white nets with long aluminum handles. Running after the fast-flying butterflies, they swooshed the nets through the air in dramatic arcs. From the sidelines this looked like strange human dance, and we couldn’t help but laugh. They handled the butterflies with deft fingers and released them after we had a good look.
Black-and-white striped Pale Swallowtails, and the black-and-yellow striped Western Tiger Swallowtails are our largest, most spectacular butterflies. Every year they fly right through my garden. In fact, I’ve observed many beautiful butterflies without even leaving home. Anise Swallowtails, Anglewings, Fritillaries, Mourning Cloaks, Skippers, Blues, Painted Ladies, Lorquin’s Admirals and Cabbage Whites have all been photographed in our backyard.
We are lucky to live here in BC, where we have 187 butterfly species; more than any province in Canada. To preserve this diversity we must be aware that habitat loss has the biggest impact on butterfly populations. We can encourage butterflies by leaving some native vegetation on our properties, and growing garden plants that butterflies favour, such as Butterfly Bush, Black-eyed Susans, Liatris, Lantana, Butterfly Weed, Purple Coneflower, and Asters. Pesticides can kill butterfly larvae, and should be avoided.
Butterflies and moths (Lepidoptera) are classified under insects (Arthropoda). Like all insects, Butterflies have a segmented body and an external skeleton called an exoskeleton. The body is divided into three parts: the head, thorax and abdomen. Lepidoptera means “scaly wings” in reference to the fact that the wings of these insects are made up of thousands of tiny scales.
Butterflies have a life history than has long fascinated humans. The life cycle starts with the female laying an egg on the under side of a leaf. Some species lay eggs singularly, while others lay in clusters. A tiny larva, or caterpillar, eats its way out of the egg, and begins to eat the plant it is situated on. As the caterpillar grows it moults. Butterfly larvae usually moult 4 times, and the stages between moults are called instars. The larva’s main purpose is to eat plant matter.
On the final moult the larva becomes a pupa, or chrysalis, which is usually attached to an object by small hooks. Over the next few weeks, hormones trigger a dramatic transformation from an immature larva to a mature adult butterfly. Internal organs develop, and wings are formed. Newly emerged butterflies remain still for a time while their wings dry and harden, and are very vulnerable at this stage. This transformation, or metamorphosis, is one of the most mysterious and compelling aspects of butterfly biology.
Adult butterflies feed by sipping nectar from flowers by using their tongue-like proboscis. While adults must feed on nectar to survive, the adult’s main objective is to reproduce. Butterflies usually mate quite soon after emerging. Males pursue females by perching or patrolling in an area where females are likely to occur. During mating, the male transfers a spermatophore, which includes sperm and a package of sodium, nutrients and protein. After the sperm is used to fertilize the eggs, the female consumes the spermatophore.
To complete their nutritonal requirements, butterflies seek out animal feces, urine, rotting carrion, wood ash and mud. Males, who lose a substantial portion of nutrients in the transfer of a spermataphore to a female, are often seen puddling together at the muddy edges of ponds and puddles. At the end of a backpacking trip last summer, we observed a large group of Swallowtail butterflies puddling at the edge of a stream.
Butterflies see the same colors that we do, but can also see ultraviolet light, which allows them to detect patterns in flowers and differentiate between similarly colored males and females. Despite this, butterflies cannot see detail from a distance, and lack depth perception. As a result, male butterflies often chase the wrong species of butterfly, and may even mistake a walking human for a potential mate. The search for a mate is narrowed down by the use of pheromones, or chemical signals. Males also determine females of the right species by their behaviour.
After mating, the female seeks out a food plant suitable for a developing larva. The female uses sight, texture and taste to determine if the plant species is suitable. She then lays eggs on the underside of the leaves, thus completing the life cycle.
In some species, this life cycle, called a “brood” is completed several times in a year. Some species live in very specific habitats, and do not range far. Others, such as the well-known Monarch butterflies (seldom seen in our area), migrate in huge swarms. Some, such as the Mourning Cloak, hibernate as adults over winter, and complete their life cycles in the spring.
Several creatures prey upon butterflies, especially birds. To escape predation, many butterflies have eyespots on the back of their wings, or tails that resemble antennae. This front to back reversal trick causes birds to target the hind wing of the butterfly, thinking it is the head. As a result, many butterflies lose a piece of wing, but their vital main body remains intact.
Every year I am struck afresh by the brilliant colours and patterns that these winged creatures exhibit. It is little wonder that butterflies have inspired humans throughout the ages.
Click on a link below to view the CVNS newspaper column.