Over the last few years we have been pleased to note an increase in the number of adult monarch butterflies visiting, and caterpillars feeding on, the milkweed plants growing along the roadside near our cottage on White Lake. While we searched for the monarch’s intermediary pupal stage, termed chrysalis, we were unsuccessful until recently. It just so happens one adventurous caterpillar decided the outside wall of our neighbour’s cottage, several hundred meters from the nearest milkweed plant, would be a good place to pupate. Courtesy of our understanding neighbours, we photographed the transformation over a couple of weeks from chrysalis to adult.
In previous articles we have featured monarch caterpillars as well as other insects, such as the swamp milkweed beetle and milkweed tussock moth caterpillar, that feed exclusively on milkweed – a plant that is toxic and distasteful to most beasties. This past summer we noted the highest concentration yet of monarch caterpillars devouring the leaves of this plant. The caterpillar, which is the larval stage of butterflies, is the growth phase. Some caterpillars increase their mass by more than 1000 times through continuous eating. When the caterpillar reaches full size, such as this individual we photographed in late August, it prepares to pupate.
Immediately prior to pupation the caterpillar stops feeding, evacuates its gut and finds a plant twig (or in the case of our subject the side of a cottage) to which it will attach itself for the sedentary pupal stage. Once firmly attached, the monarch caterpillar transforms into a chrysalis which has a transparent protective casing. Initially the chrysalis appears to be light green with several gold metallic spots. The word ‘chrysalis’ has its root in the Greek word for gold. This picture of the chrysalis, showing flecks of gold, was taken the day after it was first noticed by our neighbours.
During the pupal stage most of the larval tissues and organs are digested and reorganized into the body of an adult butterfly. As this transformation occurs over a couple of weeks the colour of the chrysalis darkens. Eventually, once the adult tissues are formed, one can see the folded black and orange wings of the soon-to-emerge adult. This chrysalis was photographed less than one hour before the adult butterfly emerged.
When ready to emerge, the adult butterfly breaks out through a split in the protective outer shell. Shortly after emerging, the butterfly holds out its limp wings and moves about to pump its “blood”, termed hymolymph, into the veins in the wings. The process is gradual with the wings first unfurling, before becoming full-sized and rigid. Until the unfurling and hardening process is complete, which in the case of this butterfly took 24 hours, the wings are not capable of supporting flight.
In our region monarchs produce two or three generations each summer. The monarch’s life cycle is unique with the summer’s last generation being programmed to migrate the long distance to central Mexico where they spend the winter months. In fact, it may take several more generations descending from ‘our’ monarch to achieve Mexico. The newly-emerged adult, below, was photographed with its wings fully extended in preparation to depart. Shortly after taking this pictured it flew off, headed south. Meanwhile many human residents around White Lake were just starting to plan their flights to warmer winter destinations.
Many readers were probably exposed to this transformation as young students by their elementary school teachers. In September, this amazing metamorphism fascinated four adult cottagers for some time, and positively mesmerized Daisy-the-cat who chattered away, as the newly-emerged adult butterfly moved around pumping up its wings.
How fortunate we are to be able to spend our summers on Three Mile Bay, White Lake.