spiracles | butterfly anatomy | butterfly physiology | metamorphosis | oxygen
Almost all living organisms on Earth require oxygen to survive. The purpose? To digest and gain energy from food. These organisms, called ‘obligate aerobes’, use external and internal body parts to uptake and process oxygen.
Humans uptake oxygen using their noses and mouths, and, we process oxygen using our lungs. Insects, uptake oxygen using spiracles (external openings on the surface of their skin) and process oxygen using tracheae (a series of internal tunnels).
But what happens when insects undergo metamorphosis? Does metamorphosis change how they uptake and process oxygen? In this post, we describe physical changes in the bodies of butterflies to reveal how they acquire oxygen through 4 key stages of their lifecycle. That is … in the egg, caterpillar, chrysalis and butterfly life stages.
- THE EGG
In the standard shell of a single chicken egg, there are on average, 8000 pores which facilitate the uptake of oxygen and release of carbon dioxide (i.e. the waste product of processed oxygen). The same principal applies to butterfly eggs. The chorion, located at the top of the egg comprises tiny pores called aeropyles and is where oxygen enters the butterfly eggshell (see image below). The delivery of oxygen facilitates the growth of the egg yolk into a caterpillar.
- THE CATERPILLAR
When the caterpillar emerges from its egg, the uptake of oxygen from the atmosphere is drawn in through its spiracles. Spiracles are usually round or oval shaped openings that exist along the length of a caterpillar’s body. They are, more or less, equivalent to human nostrils. Once oxygen enters each spiracle it flows through a series of tunnels called trachea where it is processed. As butterfly caterpillars grow, so do their spiracles and trachea, giving them the ability to take up more oxygen.
- THE CRYSALIS
When the caterpillar moults for the final time, it simultaneously lays a new ‘chrysalis’ skin around its body. For metamorphosis to be successful, supply of oxygen is extremely important. Spiracle openings are re-engineered along the length of its abdomen. Next, the chrysalis skin hardens, the caterpillar dissolves into goo, and communication between each cell ensures the re-development of trachea.
- THE BUTTERFLY
Underneath the hardened chrysalis skin, the butterfly completes metamorphosis with a new set of spiracles and trachea, once again in the location of the abdomen. Over the course of the butterfly’s life, it will uptake and process oxygen through these newly formed spiracles and trachea. Only this time, it has the ability to uptake oxygen in mid-air and at flying at speed!
Insects truly are fascinating creatures. When we actively think about physical changes insects undertake to survive, we realise they’re even more remarkable. For all insects, including butterflies, oxygen is vital. Like humans, the uptake of clean oxygen, provides healthier outcomes for growth and longevity. Needless to say, when choosing chemical sprays, paints or other potentially harmful products, it is worth sparing a little more thought on our contribution to air quality and the big-picture future of our butterflies.
