By Art Guppy
Recently, listening to the radio, I was reminded of a global event that is scarcely reason for celebration: the human population of the world has passed the seven billion mark. That information almost instantly brought to my mind a rather extraordinary incident that happened one summer about 1935 when I was a boy living at Tofino. It was when I was becoming very interested in butterflies because I was seeing a great many of them in my mother’s garden, and I was taking pride in learning to identify the various species. One especially beautiful species seemed to be missing from our garden, but I knew it should be there, for one winter’s day when I was carrying in wood for our stove, I had found a live one hibernating in our woodpile. It was a Mourning Cloak, the only live one I had ever seen.
One day several years later, my father asked me to come with him to an island in Tofino Inlet, as he had something to show me. There, on one side of a little rocky hill, several willow trees were literally crawling with slender, spiny, black caterpillars, each decorated with a row of large, reddish spots along its back. My father had recognized them as the larvae of Mourning Cloak butterflies, though he called them Camberwell Beauties, which was their name in England where he had come to know them. There were thousands of them! I happily collected several and took them home.
A few days later I returned to the island, and on the little rocky hill found a very changed scene. There was not a leaf left on the willow trees, and everywhere on the rocks black caterpillars were crawling about, obviously desperately searching for food. All of the island was thickly forested with conifers except for the little hill and a cleared grassy area, and there could be nothing under the trees or on the rocks for the caterpillars to eat. I took some more home, but there seemed no hope for the others. Willows, which are the food plant of Mourning Cloaks, were scarce at Tofino at that time, as before the village was settled, the area had been thickly forested with cedar and hemlock with no openings for willows. Fortunately, I was able to obtain food for my hungry little guests by visiting a little rocky island where there were a few shrubby willows and no spiny black caterpillars. I need to explain here, that my interest in butterflies had led to my making a collection of them, neatly pinned in a little wooden box. As I can understand the feeling of disapproval that most readers are feeling, I will come back later to the subject of collecting butterflies.
All of the rescued caterpillars were healthy and before long all pupated, so I had boxes and boxes with chrysalises hanging from the lids. I did not need to wait long to be rewarded for my rescue efforts, because within two or three weeks all the butterflies emerged and spread their beautiful wings. Two went into my collection, and I had the pleasure of releasing the others. For the rest of the summer there were always two or three Mourning Cloaks flying about my mother’s garden. What struck me as really remarkable was that every caterpillar had become a butterfly. Not one had been parasitized by an ichneumon wasp or other parasite.
Using the knowledge I had gained from raising caterpillars into butterflies, it was not difficult for me to understand the probable explanation for the population explosion on that island in Tofino Inlet. Except for a few scrubby willows on windblown rocky islands, there were probably no willows in the thickly forested area near Tofino until people cleared land for their homes and provided openings for willows to get started. Even the willows where we found the caterpillars were the result of human activity on the island. However, there would have been willows at a distance from Tofino along rivers that flowed from the interior of Vancouver Island, and likely there would have been Mourning Cloak colonies on those willows, for at that time Mourning Cloaks would have been common farther to the south and east. Evidently a female butterfly that had already mated had strayed from one of those colonies and found its way to the group of willows on the island in the inlet. Probably that was the year before we found the caterpillars. (No doubt the butterfly I had found in our woodpile a few years earlier had made a similar journey, but likely it was a male or an unmated female.)
One female Mourning Cloak lays about 100 eggs, so it could start a sizeable colony on an island where normally there were no butterflies and consequently no ichneumon wasps or other parasites that prey on butterfly caterpillars. That winter there would have been a large number of Mourning Cloaks hibernating in sheltered spots on the island, and in spring the females would each have laid about 100 eggs on the willows. It is not difficult to understand where the thousands of caterpillars came from! It is an interesting thought that the ichneumon wasp that may be the butterfly’s worst enemy, is also in a way its best friend. It was the lack of the wasps that brought disaster to those caterpillars.
I need to digress here for a moment to comment on my butterfly collecting. I would not encourage anyone today to make such a collection except for scientific purposes, but it does make a difference that my collecting activities actually added to the local butterfly population, rather than subtracting from it, because I raised far more butterflies than went into my collection. No doubt, by taking partly-grown caterpillars out of their natural habitat, I made it more difficult for ichneumon wasps to find prey, but I don’t feel very guilty about that. I am aware that my parents and my older brothers kept an eye on my activities and made sure I was doing no harm. They knew there were no rare butterflies at Tofino. It makes a big difference that at that time there were very few butterfly collectors in relation to the quite large butterfly population.
It may be that my belief my collecting activities were adding to the local butterfly population was not merely wishful thinking. When I was a young boy, there had been one other collector at Tofino, a middle-aged man who took his collecting of butterflies and moths quite seriously, and when he saw the Mourning Cloak from our woodpile in my collection, he accused me of cheating by adding a butterfly that could not have been found at Tofino. Unfortunately, that gentleman had died a year or two before the species turned up on the island in the inlet, so I never had the satisfaction of showing him those butterflies. I found it very interesting and very satisfying that in the summers that followed my rescue operation there always seemed to be a few Mourning Cloaks at Tofino. The photograph of a Mourning Cloak on page 262 of Butterflies of British Columbia and a similar photo which accompanies this article were taken in August 1968 in what had been my mother’s garden at Tofino. I like to think the butterfly in those photos was descended from the ones I rescued on the island.
It is now a great many years since my father showed me the willows alive with black caterpillars, but the memory of those unfortunate insects, having consumed all the natural resource that kept them alive, wandering hopelessly about on those barren rocks is still fresh in my mind, and I find myself wondering if I was seeing that day in microcosm the eventual end of humanity.
Not only butterflies, but almost all creatures except carnivores depend on predators to keep their populations at a healthy level, while the carnivores have their populations limited by the available supply of prey. Only Homo sapiens could be an exception to this rule. The evolution of an exceptional brain in that species could enable it to keep its population at a healthy level without being the prey of a predator, but unfortunately, that exceptional brain is of no use if it is not used. Instead, it seems that we intend to be our own predator, and have invented nuclear bombs as an efficient method. Surely it would be better if we learned from nature and used our brains to avoid the mistake made by the Mourning Cloak butterflies when they laid too many eggs on that little group of willows.
A clarification: If you have read about Mourning Cloaks in Butterflies of British Columbia by Crispin Guppy and Jon Shepard, you will have encountered a different description of the island in the above story. I gave Cris the information over the telephone, and details can get scrambled during a phone conversation. The island was as described above. I know. I was there.