We left off on our monarch adventure with a 5th instar caterpillar in a J-hang position ready to head into the next phase of his or her life cycle. You can read about how I started on this journey of raising monarchs in Part 1 of the series (https://doctorb.blog/2019/08/06/raising-monarchs-part-1/) and the first two life stages in Part 2 (https://doctorb.blog/2019/08/12/raising-monarchs-part-2-the-egg-and-the-caterpillar/). Although watching the speed at which the caterpillars grow was completely amazing, this next phase – the chrysalis – is the most mysterious and magical part.
So with the last pair of prolegs grasping the little silk pad that the caterpillar had made, he or she shed her larval skin for the final time and officially entered the pupal stage. Although it is this shedding of the skin and forming into a chrysalis that marks the beginning of this new life phase, in truth tiny clusters of cells that would eventually give rise to the adult structures had been organizing within the caterpillar’s body for some time. As the chrysalis takes shape, a stem comes from the cremaster on the hind end of the caterpillar and stabs into the silk pad creating a strong anchor that will hold the pupa in place for the duration of this stage. It is important to note that unlike many other insects, such as moths, that spin a silk cocoon in which to pupate within, butterflies do not form a cocoon. The monarch chrysalis is breathtakingly beautiful! It is surprisingly small given the size of the adult monarchs that emerge from it, measuring only about 3 centimeters in length, and a lovely light jade green colour. But it is the small gold dots that decorate the outside that make it particularly striking. Like all things in nature, the beauty is not for our benefit – I have read that the gold dots reflect light therefore making the chrysalis harder to spot. Camouflage is important at this phase given that the pupal is immobile and therefore very vulnerable.
The pupal stage for monarch butterflies will last from 8 to 15 days under normal summer conditions. And although just seeing them is inspiring, I wanted to learn what is actually going on inside. How does it get from a caterpillar body into an adult butterfly? Basically the caterpillar releases enzymes that digest all of it’s body, turning it into a proteinaceous soup – or goo. Well almost all of it’s body. What remains after the digestion process is those tiny clusters of highly organized cells, called imaginal discs. These discs then begin to rapidly divide and expand, using the protein and energy from the larval soup to fuel the process. And each disc will give rise to a different adult structure, such as an antenna or eye or wing. One of the very last processes to occur is the development of pigment and the chrysalis will appear to turn black and then just a short time before emergence the orange, black and white pattern of the wings will be seen through what was actually a transparent case all along.
Once pupation is complete the pupal case splits open and the adult butterfly emerges. The wings are floppy and wet and the abdomen is very distended. Over the next few hours the butterfly will cling to the empty case and the hemolymph (insect blood) will be pumped out of the abdomen and through vessels into the wings. The wings will take their shape, dry out and harden in preparation of flight. The first flight will be to a flower to fuel up on some nectar. Even though monarch caterpillars are highly specialized, feeding ONLY on milkweed plants, the adults are generalists – meaning they will visit a variety of flower species to consume the nectar.
Like the caterpillar stage, the adult butterfly has three body parts: head, thorax and abdomen. Monarch butterflies have very tiny front legs that curl up, giving the appearance of being 4-legged when in actuality they do have 6 legs like all other insects. Their tongue is a straw-like proboscis that is normally held in a curled up position but will extend to probe down into flowers to suck up nectar and water. Adult males are easily distinguished from females as they have a black spot on one of the veins on their hind wings. These spots contain specialized scales that produce a chemical important for a variety of butterfly and moth species during courtship. Interestingly, although the male monarchs have these scales it does not appear to play a role in their courtship of the female monarchs. During the summer time adults will typically live two to five weeks with their main goal being reproduction. In late summer and early fall the winter generation of butterflies will emerge. These adults will look visually like their summer counterparts, but their reproductive organs are not mature. They do not focus on reproduction, but rather on making the long journey south to their over wintering grounds. For monarchs on the eastern side of Canada this means flying to central Mexico. Monarchs on the western side will overwinter in California. The winter monarchs are able to live for 8-9 months, and once spring hits and daylight increases their reproductive organs will mature and the life cycle will continue.
It was an amazing experience to watch the chrysalis change from green to bluish to black and then to finally see the adult wings within. The kids and I excitedly hovered around watching as they emerged and prepared their bodies for flight. And it was a wonderful feeling seeing the adults take off – fluttering over to the meadow next door where a buffet of flowers awaited them. Now as the days are getting shorter and the air has a chill to it I still see the occasional monarch soaring about. It gives me pause to wonder about the monarchs we raised and how far south they are now. I am grateful that the kids and I took the time to care for and observe these majestic creatures and dreaming about the butterfly garden we will create next year.