Life Cycle of a Butterfly "Metamorphosis"
What we tend to overlook, when we are first attracted to butterfly observation, is that the butterfly is the result of a much longer journey......a journey that is quite different from that of many creatures on this planet. The flight stage is the final statement......the last hurrah so to speak.
No doubt that during your early adventures you will become increasingly aware of these other facets of a butterfly's life span but for many these stages remain a mystery. Actually what occurs prior to the flight stage of development is by far more intriguing and captivating. As you gather information on the stages of butterfly development, scientifically known as metamorphosis, please keep in mind that the way in which it ultimately plays out can be species specific.
Egg Larva Pupa Butterfly
Obviously newly hatched caterpillars are minute little creatures, some virtually invisible to the naked eye but they are eating machines that grow very quickly. Growth does not occur during the flight stage. It is done strictly while in the larva stage and they can multiply in size by more than a thousand fold in no time. In a matter of a few weeks they can go from an egg, to a caterpillar, to a chrysalis, to another egg laying butterfly. For some species this process occurs only once during our season but for others two or three cycles can be completed before diapause, hibernation or migration must occur.
It all starts with the eggs which are very tiny to microscopic and generally, but not always, laid on the underside of host plant leaves either singly or in clusters. Host plants are located by the adult butterfly's ability to distinguish the plant's chemical signature. For many species the growing season for their host plants can extend for many months allowing for multiple broods.
Eggs may also be deposited near the area in which the host plant may be found. This condition arises when specific host plants have died off at their season end and the eggs are required to overwinter in order to take advantage of the following season's crop. So, depending on the time of year the eggs are laid will dictate when the eggs are predetermined to hatch. If they are laid early enough in the season they will come full term usually within a week or so, again depending on the species. If they are deposited late in the season the eggs may be required to wait until the following season to complete the remainder of the journey. An example of this scenario is best demonstrated by many of the Fritillaries that feed exclusively on violets. These violets die off part way through the Fritillary's flight season thus the eggs of the last brood are required to over winter in order to take advantage of the following seasons crop of their sole host plant.
As a caterpillar their appearance can be even more diverse than in their final stage as a butterfly. They can be naked, hairy or have varying amounts of bristles or spike like appendages adorning their tubular form. Colours range from dull bland singular colours, that serve to camouflage, to mixtures of bright stripes or blotches that serve to warn. Essentially they are harmless even though they can appear to be quite menacing.....like the Swallowtail caterpillars. Some are distasteful and others poisonous to predators as is the Monarch, Cabbage White and Pipevine Swallowtail caterpillars. Caterpillars of this type are usually brightly marked to serve as an unmistakable reminder that they should be avoided. Never-the-less, it is this stage that tends to go largely unnoticed as they go quietly about their business.
Throughout the larval stage a caterpillar has to shed it's skin several times in order to accommodate further growth. The time between these sheddings is called an "instar" of which there are usually an average of five and spans two to four weeks. When we use the term a "third instar" caterpillar we are saying that it has shed twice. Immediately upon shedding it's old skin the larva fills with air. This allows the new skin to take on that size giving the caterpillar as much room as possible to grow into this new size. After each of these transformations it is possible that the caterpillar can be a different colour or appearance from the time before. Therefore, depending on which instar a caterpillar is in, understanding the instars can play a roll in the identification process.
When the final instar occurs what emerges is the pupa, which when completed, usually resembles part of the plant they are on........this serves as camouflage. This stage may last a week or so at which time the final stage an adult butterfly is produced, that either carries on the next generation locally or migrates, like the Monarch, to warmer climates before winter. Or they might over winter in this stage and emerge the following season to complete their predetermined task. In any case the transformation, while in the pupa stage, is truly a miracle. What emerges from this case in no way resembles the caterpillar that produced it. Basically what happens is the complete disassembly of the cells that made up the caterpillar and the reassembling of those cells into it's new form....a butterfly. Upon emergence the swollen body immediately begins to pump fluids into the tiny shrived up wings. Within a couple of hours the wings are full size, dried, become more rigid and are capable of flight.
A few varieties, such as the Mourning Cloak or Compton Tortoiseshell, choose to hibernate here as adult butterflies and complete their cycle the following season. Others, like the Crossline Skipper, overwinter in their larval stage and some Elfins do so during the pupa stage. Still another way to beat winter is to do so as an egg as with the Bog Copper. Some Hairstreaks do this but they have an obstacle to overcome by choosing this method. As you are now aware eggs are laid on or near host plants so when the eggs hatch the food supply is right there. Since Hairstreak hosts are trees, rather than plants and if the eggs were laid traditionally on the leaves, they would fall to the ground in the fall presenting a food source proximity problem the following spring. This is overcome by depositing the eggs on the buds at the base of the leaf stem so the egg will remain in the tree close to the food source when the time is right.
These timelines can be complex and require a little more determination to follow in their entirety but it is very rewarding to observe the slightly different approaches to all four stages of the journey. As you can see from this page all butterflies follow the same scenario but not necessarily the same timeline when confronted with a seasonal environment. Even within the same species and the same season the timeline can vary between broods. Adaptation is the key to survival for any butterfly.