Post 7

           Life poses many questions about why we’re here and how we are what we are.  An example with several very vivid stages is the metamorphosis of a caterpillar into a butterfly.  Two insects that are so distinguishably different were once the same.  An overview of the four stages of a caterpillar’s life will shed light on the process it undergoes in the occurrence of metamorphosis.

Stage 1:

The first stage of a caterpillar’s life is the egg.  When it comes to where to lay them, the mother butterfly must find a plant that the specific species eats.  This is referred to as the host plant.  Caterpillars are extremely picky about their diet, and usually only eat one type of plant.  So, as soon as the butterfly finds an accommodating host plant for her eggs, she lays them and leaves them to defend for themselves. 

Stage 2: Birth

The next stage is the larval period, or more commonly referred to as the caterpillar.  During this period, the larva is subjected to 5 steps of molting in order to transform.  Each time the caterpillar molts, it is referred to as an instar.  Three to seven days after the eggs are laid, the larva hatch, and are in the form known as first instar.  A caterpillar’s objective is to eat, in order to grow and become a butterfly, and the process before doing so takes 2-5 weeks depending on conditions.  Varying upon the species, the larva will eat the egg’s hard shell for sustenance, or they will start eating the host plants.  The excessive eating causes the larva to become too big for it’s skin, so it grows a new one underneath the old, and then proceeds to molt out of the smaller skin.  This is referred to as the second instar.  The third instar is much like the second, with the only difference being that the caterpillar has once again increased in size.  In both these steps, the caterpillar appears to look like bird droppings in order to protect itself.  The caterpillar continues to grow, and molts again.  The insect with its new skin is referred to as a fourth instar caterpillar.  A caterpillar this far into its transformation begins to change color and has a more “smooth” appearance, like a snake.  The change in appearance facilitates the camouflage function to make it look like the host plant.  The final step, known as the fifth instar is the last time the caterpillar will molt, and is now ready to pupate and become a butterfly.

Stage 3: Transformation 

The third stage is the chrysalis; the caterpillar will mummify itself in preparation for its metamorphosis.  The caterpillar will attach itself to the base of a plant’s stem, and then proceed to spin a silk thread around itself to hold the chrysalis in place.  Meanwhile, underneath the caterpillar’s skin, the pupal shell begins to develop, and depending on the species it takes many different forms.  This is what defines what the butterfly will look like.  Once securely in place, the exoskeleton will spilt open, and expose the pupa.  The average time in the chrysalis stage is about one to two weeks, varying with the species. 

Stage 4: Rebirth

After climbing out of its old body, the final stage is complete; the caterpillar is now a butterfly.  The butterfly is still not yet ready to fly away and start its life.  The cramped conditions of the previous body cause the butterfly’s wings to be crumpled and wet when it emerges.  It will hang off a branch with its wings down, and will begin to pump fluids to the veins in its wings by flapping them.  The wings become fully straightened out through this instinctual process, and then the butterfly must wait several hours for its wings to harder.  Now, the new butterfly may spread its wings and take off. 

The sole purpose for this incredibly elaborate 5-stage process is to reproduce, to spread ones genes in distant places.  With the average lifespan of a butterfly being about two weeks, they don’t have a single second to spare!