Will modern-day insects grow to massive size in a high-oxygen environment?

Question

It's a reasonably well-known fact that insects grew to massive sizes due to the excessive concentration of oxygen in the prehistoric-Earth's atmosphere.

If one were to try to recreate this high-oxygen environment in a lab setting, would insects reared within grow to massive size?

Answer 1

While @CalendarJ comments "Yep!" above, a quick search suggests that experimental hyperoxia typically only increases insect body sizes slightly. Everything below is from VandenBrooks et al. 2012 (of course there could be other sources that contradict this!)

A few beetles have been reported to reach larger sizes when reared in hyperoxia, but most of the species examined reach similar body sizes in 40% oxygen as in normoxia (Harrison et al. 2009).

and:

Here we investigated the impacts of Paleozoic oxygen levels (12–31%) on the development of Blatella germanica cockroaches. Body size decreased strongly in hypoxia, but was only mildly affected by hyperoxia.

and this figure:

These results show that male cockroaches grow much larger under present-day (normoxic; 21% oxygen, highlighted box) and elevated (hyperoxic; >= 24% oxygen) levels than under low (anoxic; 12%) conditions, but the hyperoxia-grown roaches are only a bit larger than normoxia-grown ones. (Similar results for females not shown.)

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VandenBrooks, John M., Elyse E. Munoz, Michael D. Weed, Colleen F. Ford, Michael A. Harrison, and Jon F. Harrison. “Impacts of Paleo-Oxygen Levels on the Size, Development, Reproduction, and Tracheal Systems of Blatella Germanica.” Evolutionary Biology 39, no. 1 (March 1, 2012): 83–93. https://doi.org/10.1007/s11692-011-9138-3.

Answer 2

I think you perhaps have a misconception. Body size is mainly controlled by genetics, thus we have species of "bugs" that are very small, others from closely-related lineages that are much larger. Take for instance flies, which come in sizes from fruit flies through house flies up to horseflies. They're all pretty similar (under magnification) to a non-specialist, yet it seems unlikely that raising a fruit fly in an oxygen-rich environment would make it grow to the size of a house fly, let alone a horse fly.

It doesn't take much thought to come up with many similar examples, such as beetles and butterflies, with species that come in a range of sizes. It seems obvious that they've evolved a size which fits their evolutionary niche, and if they grew too large, they would be unlikely to survive.

Oxygen concentration is one of the factors that puts limits on the size of insects, but to get real size increases, you need to evolve new species that take advantage of increased oxygen, not just grow your 1st generation offspring.

Answer 3

The latest documentary I watched about the Meganeura (a giant Dragonfly from Pre-Cambrian) seems to confirm your intuition.

Based on experiments by John VandenBrooks at Midwestern University, with bugs in conditions A with less oxygen than current Earth atmosphere, and a 31% oxygen atmosphere in conditions B:

The bugs from group B were roughly twice as big. It was a bit frightening. (I don't know if there's a paper that shows the size difference statistics for several individuals.)

Here's the documentary for French TV "Science Grand Format":

• there is a lightweight interview of the scientist at 06:15
• experiments on cockroaches at 06:50
• they show the bugs different sizes at 7:45.