More Oxygen in the Air Makes for Bigger Palmetto Bugs

Jan 20, 2017

Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Usually after several hard frosts, we get a break from cockroach surprises in the kitchen. So I was surprised when a huge palmetto bug ran across the pantry shelf last week. But it could have been worse.

As plant growth surged during the Carboniferous era, the percentage of oxygen in the atmosphere reached 35% compared with 21% today. Insects rely on passive movement of atmospheric gases through openings in their body to get oxygen for metabolism – with higher amounts of oxygen available, some insects got a lot bigger back then. At the Elmo site in Kansas, a rich deposit for ancient insect fossils, scientists discovered a relative of today’s dragonfly with a wingspan of over two feet! With the decline of atmospheric oxygen levels and the rise of flying dinosaurs and eventually birds, insect size has fortunately decreased – but those roaches are still too big to suit me.