For hundreds of millions of years, insects have been remarkably successful.
They can fly, burrow, and swim. They live inside plants, on plants, beneath rocks, in soil, in freshwater and almost everywhere else imaginable.
Today, more than a million insect species have been formally described.
Yet the further back we travel, the stranger their story becomes.
The earliest chapters of insect evolution are largely missing from the fossil record. There is a notorious gap between the earliest evidence of hexapods and the much richer Carboniferous record.
Now a newly described fossil from Texas is helping fill part of that gap. And it doesn't look quite like the insect evolutionary story we might expect.
The creature, named Chosha praecursor, lived approximately 324 million years ago during the Late Mississippian Epoch.
It possessed recognisably insect-like features, including an ovipositor and terminal filament.
But it also had something modern insects don't have: multiple segmented limbs along its abdomen, modified into paddle-like structures.
Those strange appendages appear to have been adapted for life in water.
If the interpretation is correct, one of the earliest uncontested insects wasn't simply an early version of a modern terrestrial insect.
It was something considerably stranger.
The problem with the insect family tree
The evolutionary history of insects is deceptively difficult to reconstruct.
We know that insects are ancient. We know that molecular-clock studies can place important divergences surprisingly far back in time. And we know that the fossil record becomes dramatically richer later on.
But those three pieces of evidence have not always fitted neatly together.
The earliest stages of insect evolution fall partly inside what researchers have called the "hexapod gap" — a poorly sampled interval in which molecular evidence suggests important diversification was already occurring while convincing fossils remain scarce.
That creates a peculiar situation. Scientists can infer that something must have been happening. But the actual organisms responsible have been difficult to find.
The new fossils don't solve the entire problem. They do, however, provide something that evolutionary reconstructions desperately need: actual bodies.
Meet Chosha
The fossil comes from the Tesnus Formation in Texas. Chosha praecursor was not a giant dragonfly or an enormous Carboniferous predator. It was a much more primitive creature.
Its importance lies in its anatomy. Researchers identified several characteristics that support its placement among early insects, including an ovipositor and terminal filament.
But its abdomen carries the feature that immediately makes it unusual.
Instead of resembling the streamlined abdomen of modern wingless insects, it possessed multisegmented abdominal legs with paddle-like modifications.
Some of these structures also show characteristics interpreted as gill-like. Taken together, the anatomy suggests that Chosha may have lived partly in water.
That is a remarkable possibility. The insect story may not have begun with animals simply emerging onto land and then progressively acquiring increasingly specialised terrestrial adaptations.
At least some early insects may have retained — or evolved — bodies suited to environments that crossed the boundary between land and water.
An insect that looks unfinished
There is an important trap here. It would be tempting to describe Chosha as an "unfinished" insect.
That would be misleading.
Evolution does not work towards a finished design. There is no evolutionary blueprint requiring an insect to eventually become a beetle, bee, butterfly or dragonfly.
A creature's anatomy is a consequence of its ancestry and the environments in which its ancestors survived. If paddle-like abdominal limbs worked, there was no evolutionary requirement to replace them with the body plan of a modern insect.
The real significance of Chosha is therefore not that it was primitive in the everyday sense.
It is that the range of possible insect body plans appears to have been broader in the deep past than the modern survivors suggest. That is a very different proposition.
The fossils that vanished
The researchers didn't stop with Chosha. They also reassessed several other enigmatic hexapod fossils, including the Devonian organism Leverhulmia and two previously undescribed Carboniferous fossils from the famous Mazon Creek Lagerstätte in Illinois.
Together, these fossils reveal what appears to have been considerable diversity among early wingless insects and insect relatives.
They weren't simply copies of one ancestral body plan.
Different lineages were experimenting with different arrangements of limbs and other anatomical structures.
Some survived. Most didn't.
And that creates an important evolutionary illusion: if we look only at modern insects, we see the survivors.
That can make evolution appear much more linear than it really was.
Polarized-light imaging
Polarized-light imaging made fossils that were already present in rock much easier to see, photograph and identify—and in some cases revealed details that ordinary lighting almost completely hid.
This is particularly useful for compression fossils, where an insect was flattened between layers of sediment and its remains became a very thin, dark film.
Imagine a tiny fossil insect pressed into a slab of rock: the fossil may be only a fraction of a millimetre thick.
Its organic remains can have almost the same brightness or colour as the surrounding rock and the rock surface itself can be highly reflective. Normal illumination produces glare that overwhelms the insect.
Researchers working with fossil insects from places such as Florissant, Colorado found that even when organic material was exceptionally well preserved, photographs could show very little contrast between the insect and the surrounding matrix.
Then they add polarized light.
A polarizing filter selectively blocks light travelling in particular orientations.
The practical effect is surprisingly simple: ordinary light → lots of reflected glare → fossil difficult to distinguish.
But, polarized light → glare suppressed → fossil stands out against the rock.
Researchers can rotate the polarizing filter to find the orientation that produces the strongest contrast. In Florissant fossils, this can make the preserved body, wings and other structures dramatically more visible.
Why does that matter for identifying an insect?
The important information isn't necessarily the outline of the insect. It's the tiny anatomical features.
For example, researchers may suddenly be able to distinguish: wing veins, antennae, hairs, body segmentation, even patterns on wings
Those features can determine whether a fossil belongs to a particular insect family, genus or species.
And there's another interesting trick
Researchers don't necessarily choose polarized light OR normal light.
For some Florissant insects, the best documentation is actually a combination: Polarized, high-angle lighting — suppresses reflections and reveals the fossilised organic material.
Low-angle/tangential lighting without polarization — creates shadows that reveal impressions and surface relief.
The two photographs contain different information, so combining them gives researchers a much more complete picture of the insect.
It can even work inside amber
Polarized light can produce another effect with insects trapped in amber. An inclusion can distort the surrounding amber slightly, producing a stress/strain field around the insect.
Under crossed polarizers this can appear as a bright halo, making the inclusion easier to locate and examine.
That's particularly interesting because amber can preserve insects in extraordinary detail—sometimes down to microscopic surface structures.
The key point is:
Polarized-light imaging doesn't magically create a fossil. It changes the way light interacts with the fossil and its surroundings, allowing structures that were effectively invisible under ordinary illumination to emerge.
And that's why a slab that looks like just a piece of rock to the naked eye can, under the right imaging technique, turn out to contain an exquisitely preserved ancient insect.
Evolution has no obligation to preserve the weird
Imagine looking at the history of cars but destroying every vehicle except those still represented on today's roads.
Future researchers might conclude that cars evolved through a relatively straightforward progression toward the vehicles we currently recognise.
They would miss the enormous number of abandoned designs; steam cars, three-wheeled experiments, amphibious vehicles.
Evolutionary history has the same problem. The living world is not a museum containing every design ever attempted. It is a collection of survivors.
The fossil record occasionally gives us a glimpse of the abandoned alternatives.
Chosha may be one of those glimpses.
But were insects really aquatic?
This is where caution matters. The fossil does not come with a label saying "aquatic insect." The interpretation is based upon anatomy.
The paddle-like abdominal appendages and apparent gill-like structures provide evidence consistent with a semi-aquatic lifestyle.
The researchers therefore propose that at least some early stem-insects could have occupied aquatic or amphibious environments.
That does not establish that insects originated in water. It also doesn't mean that all early insects were aquatic.
One unusual animal cannot reconstruct an entire evolutionary transition. But it can destroy assumptions. And that may be more valuable.
The terrestrial revolution may have been messier than we thought
One of the major questions in insect evolution is how insects became so successful on land.
Today, terrestrial insects dominate enormous numbers of ecological niches. But the earliest stages of their evolution occurred while terrestrial ecosystems were undergoing profound changes.
Plants were also transforming landscapes. Forests were developing. Soils were changing. And freshwater environments were also becoming increasingly complex.
Arthropods were already experimenting with different ways of exploiting these environments.
The transition from aquatic or semi-aquatic environments to fully terrestrial lifestyles may therefore have involved considerably more evolutionary experimentation than a simple "water to land" narrative suggests.
The fossil evidence now hints that some of these experiments left strange anatomical traces.
And then there were the giants
There is another reason the ancient insect story can be deceptive. When people imagine prehistoric insects, they often think of gigantic dragonfly-like creatures. And those really did exist.
The famous Meganeuropsis may have had a wingspan approaching 71 centimetres, with an estimated body mass of around 100 grams.
A new 2026 study has challenged the longstanding explanation that enormous insects could exist primarily because Carboniferous and Permian atmospheric oxygen levels were unusually high.
Researchers examined the tracheolar systems supplying flight muscles in 44 living insect species across 10 orders and compared the relationship with body size, extending the analysis to the extinct giant Meganeuropsis.
Their results argue that oxygen diffusion through the tracheolar-muscle system does not by itself impose the maximum body-size limit traditionally proposed.
That doesn't mean oxygen had nothing to do with prehistoric insect gigantism. It means the familiar explanation may be incomplete.
Once again, the evolutionary story turns out to be less tidy.
Even the earliest insects were already diverse
The fossil record has repeatedly produced surprises like this. A 2012 Nature study described Strudiella devonica, a remarkably complete insect from approximately 365 million years ago.
Its existence helped narrow a major gap in the fossil record and indicated that significant insect diversification had already taken place during the Devonian.
Other fossils have revealed unexpected early diversity among insects that eventually evolved complete metamorphosis.
Some Carboniferous fossils already possessed characteristics associated with lineages that would later become enormously successful, despite their small size and their existence millions of years before those groups became dominant.
The exceptional Middle Triassic insect assemblage at Monte San Giorgio, approximately 239 million years old, contains representatives of at least 15 major insect clades.
Among them are freshwater dragonflies and caddisflies, terrestrial bugs and wasps, beetles, monurans and unusual cockroach-like forms.
The message is becoming increasingly difficult to ignore. The ancient insect world was not primitive in the sense of being simple. It was different.
What happened to all the experiments?
This may be the most interesting question. Why do modern insects mostly share a relatively familiar set of body architectures when their ancient relatives appear to have experimented with considerably stranger arrangements?
The obvious answer is extinction. Mass extinctions repeatedly removed entire branches of the insect tree.
The end-Permian event was particularly important.
Research into the global insect fossil record has found a major increase in extinction around the Permian-Triassic boundary, followed by later diversification.
The organisms that survived were then able to diversify into the newly available ecological space.
That creates a phenomenon evolutionary biologists call selective survival. The survivors are not necessarily the most advanced organisms. They are simply the lineages that happened to survive the particular combination of environmental changes, ecological competition and chance.
The evolutionary tree may be hiding a forest
There is a deeper implication. When researchers construct evolutionary trees, they are usually trying to establish relationships between known organisms.
But extinct branches are inevitably underrepresented. The fossil record is incomplete. Soft-bodied animals are particularly difficult to preserve. Small insects can be destroyed before burial. Many environments simply don't preserve them.
And even when fossils survive, their anatomy may be compressed, distorted or incomplete.
This means the evolutionary tree we construct from available evidence may be missing enormous numbers of branches.
The strange thing isn't necessarily that Chosha is unusual. The strange thing may be that we have found so few organisms like it.
A different way to think about insect evolution
Perhaps the ancient insect world wasn't a straight road leading towards the insects we know today. Perhaps it was a sprawling evolutionary experiment.
Some lineages developed wings, yet others remained wingless. Some explored freshwater whilst others became terrestrial specialists. Some developed extraordinary feeding structures. Whereas others retained combinations of primitive-looking features for millions of years.
Eventually, the survivors became the insects we recognise.
But the evolutionary history of insects wasn't written by the winners alone. It was also written by everything that disappeared too.
The insects that don't fit
There is a temptation whenever a new fossil is discovered to ask: "Where does it fit?"
But perhaps there is another question worth asking: Why doesn't it fit the modern picture?
Chosha matters precisely because it doesn't look like a straightforward precursor of anything alive today.
Its paddle-like abdominal limbs suggest an ecological experiment that left no obvious modern equivalent. Its anatomy demonstrates that early insect morphology could differ substantially from the body plans familiar from living insects.
And the other fossils examined alongside it suggest that such unusual experimentation wasn't necessarily an isolated event.
The lesson isn't that evolution is wrong. It is almost the opposite. Evolution may have been far more inventive than the surviving evidence allows us to see.
The insects around us represent only one surviving branch of an ancient experiment involving hundreds of millions of years of extinction, adaptation and chance.
Somewhere in the rocks are the bodies of the experiments that failed. And occasionally, one of those forgotten experiments turns up in a slab of ancient rock.
It doesn't fit the story. It forces us to rewrite it. And that may be exactly what fossils are supposed to do.
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