What are the tiny holes for?
Monarch biologist Dr. Karen Oberhauser explains: "Monarchs 'breathe' through tiny openings on the sides of the abdomen and thorax called spiracles. The spiracles are in their cuticle, like our skin. The reason that I put quotes around the word 'breathe' is because this is very different than the kind of breathing you do. Monarchs don't have lungs. The air goes into their spiracles and through a whole series of tubes in the body called trachea. The trachea carry oxygen throughout the monarch's body."

"Insects are limited in size because of this inefficient system of air exchange," says Dr. Lincoln Brower. Insects cannot be more than about 1 inch thick. "Insects could be the size of Sherman tanks and dominate the world if they had our mode of respiratory system!" he exclaimed.

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