Looking back in history, there is one thing that you might notice about the creatures we know today as insects – They were huge! Many fossils have revealed that insects used to have wingspans of up to one foot in length! There were even beetles that were the size of dogs. Nowadays, when you picture an insect, you likely picture a creature that is no bigger than the size of a penny.
We are not the only ones who have wondered about this size comparison. Scientists around the world have devoted lifetimes of studies on why insects are so small in the modern world. They have explored the evolution of the species, along with the development of the atmosphere that we live in. They have also taken into consideration the interaction that insects have had with other species.
Oxygen is Essential
National Geographic explains why prehistoric insects may have grown rapidly from the oxygen levels on Earth (https://news.nationalgeographic.com/news/2011/08/110808-ancient-insects-bugs-giants-oxygen-animals-science/). While this created some impressive varieties of the species we know today, it was not necessarily an easy task. Recent studies have suggested that the bugs got so big during these times because there was an excess of oxygen in the atmosphere. They grew and expanded in order to avoid becoming poisoned by the air.
There were vast swamplands that covered the ground, expelling oxygen levels of around 30%. This is up to twice as high as the current oxygen levels that we are used to today! This rich environment was key to why the bugs were able to keep growing while also maintaining their energy levels.
It can also be noted that larvae are most sensitive to oxygen intake. At this stage, the creatures absorb oxygen directly through the skin. Since there was an abundance of it millions of years ago, larvae were receiving it in abundance. The thought that larvae also receiving oxygen from water meant that they needed to grow even more rapidly to adjust to the levels they were receiving. “If you grow larger, your surface area decreases relative to your volume,” Dr. Verbek, study co-author of Plymouth University in the UK, writes.
They Come in Masses
If you think about insects, you probably don’t think about 1 or 2 at a time. According to Best Pest Control Boston (http://bestpestcontrolboston.com/), whose expertise is pest control in Boston, insects come in groups, large quantities that are usually thought of as a nuisance rather than an impressive feat. While oxygen is thought to have been the main culprit in insect growth, there is also the notion that there is power in numbers.
As insects began to grow larger, so did the rest of their species and subspecies. Pretty soon, they had created an army of gigantic proportion. Ask an Entomologist explains, as the insects continued to grow, they also began to dominate (https://askentomologists.com/2017/03/28/is-oxygen-the-reason-insects-were-so-big-way-back-when/). With their larger size, they were able to easily take down their prey. There is also the thought that larger animals could not take them down as easily because they were becoming much larger than normal. During this time millions of years ago, insects were thriving.
Skeptics point out that oxygen could not have been the only factor for insect growth. Not every species that lived in the area were giant. Comparing fossils to the insects that we are used to today, we can see that there were still some varieties of tiny bugs as well. An observation was done on the trachea and how it is used for oxygen intake.
As predicted, not all insects are going to share identical trachea. The ones who used their trachea up to 40% naturally grew larger because of the abundance of oxygen. Some bugs only use 2% of the trachea, as you can conclude, massive difference in growth.
Forbes explains that there has been a decline, and is still a current decline, in Earth’s oxygen levels (https://www.forbes.com/sites/trevornace/2016/09/27/earths-oxygen-levels-declining-scientists/#1fcb083d7e4d). This is happening at the present moment, and some scientists are baffled by it. Data has been taken by air bubbles that have appeared in glaciers on Greenland and Antarctica.
The results show that the atmosphere’s oxygen has declined by 0.7% and continues to decline. Global erosion rates have been tied to the loss of oxygen. Another factor appears to be the rapid glacial to interglacial periods that we have been experiencing.
Luckily, this is not enough to create significant problems for life on Earth; it has just resulted in some evolutionary adjustment. There have been some dramatic shifts in global temperature, but those who live on the planet will continue to adjust and evolve. The way that the Earth continues to develop is studied by scientists daily, providing these answers to our curiosities.
While it would have been fascinating to witness massive beetles and dragonflies the size of seagulls roaming around, they are clearly not a fit for the atmosphere that we live in today.