Eventually, when oxygen is set at a critically low level, they can't even get off the ground. Like the hoppers, dragonflies perform better with increased oxygen, flying more energetically and breathing faster. Whether or not the Paleozoic oxygen pulse actually triggered the rise of insect gigantism, Harrison is motivated by the more general applications of his work. There is a tight relationship between body size and metabolic rates in all animals, but no one has been able to determine why this is so. From insects to elephants, the pattern is impressively consistent.
Smaller species tend to live fast and die young.
They have speedy metabolic rates and short life spans. Bigger animals are generally longer-lived, and they have more leisurely metabolic rates. Since high metabolism demands high oxygen delivery, Harrison suspects that respiratory mechanisms may provide some valuable clues about the nature of this basic relationship. Harrison plans to examine insect flight at higher altitudes, where oxygen naturally decreases. For this work, the record-setting metabolic rates and flight abilities of bees make them natural subjects.