Planet Earth

Attack of the Giant (Extinct) Insects!

They just don't make two-foot dragonflies like they used to. Here's why.

By Jocelyn RiceNov 2, 2007 12:00 AM

Newsletter

Sign up for our email newsletter for the latest science news
 

At the tail end of the Paleozoic Era, dragonflies with two-foot wingspans cruised through swamps, and five-foot-long millipedes crawled along the forest floors. Today the largest insect is a beetle no larger than a computer mouse.

Bugs used to be bigger, in part due to higher concentrations of oxygen. Unlike vertebrates, insects absorb oxygen directly through networks of air tubes. To find out how this mode of oxygen transport affected the size of insects, researchers at Argonne National Laboratory X-rayed beetles large and small. They found that the bigger the bug, the greater the proportion of the body dedicated to air tubes. Getting oxygen to the beetles’ legs was particularly constraining on size, however. In order to absorb enough to survive in today’s atmosphere, a beetle rivaling the size of its prehistoric ancestors would need tubes bigger than its leg openings could hold.

1 free article left
Want More? Get unlimited access for as low as $1.99/month
Already a subscriber? Log In or Register
1 free articleSubscribe
Want unlimited access?

Subscribe today and save 70%

Subscribe

Already a subscriber? Log In or Register
More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Join
Our List

Sign up for our weekly science updates.

 
Subscribe
To The Magazine

Save up to 70% off the cover price when you subscribe to Discover magazine.

Copyright © 2021 Kalmbach Media Co.