True water bugs have thrived in aquatic environments for over 250 million years

Nature · Published 3 October 2026 Swipe more like this →

In short: Known as Nepomorpha, these insects have mastered life in freshwater across the globe. From tiny boatmen to giant predators capable of hunting fish, they have evolved specialized mouthparts and hidden antennae to dominate their watery domains. Their ancient lineage stretches back to the Triassic, surviving through remarkable evolutionary adaptation.

The infraorder Nepomorpha, commonly referred to as true water bugs, comprises approximately 2,000 species found worldwide, excluding polar regions. These insects belong to the suborder Heteroptera and are distinguished from their relatives by their vestigial or entirely absent ocelli. Historically known as Cryptocerata, or the hidden-horned ones, they possess reduced antennae that are typically tucked against the head, a feature that reflects their specialized aquatic lifestyle.

Most Nepomorpha inhabit freshwater, though the superfamily Ochteroidea prefers the water's edge. As predators, they use a rostrum to pierce prey, consuming invertebrates and occasionally small fish or amphibians. While many suck fluids, some species like the Corixidae can chew their food into a pulp. Their defensive capabilities are significant; the common backswimmer, Notonecta glauca, can deliver a sting to humans that is often described as more painful than that of a bee.

The evolutionary history of these insects began around the start of the Early Triassic, roughly 250 million years ago. Fossil evidence, including the advanced Triassocoridae and the primitive Lufengnacta, suggests that the radiation of modern superfamilies was largely complete by the end of the Triassic, about 201 million years ago. While the classification of higher taxa was once a subject of intense debate, modern cladistic analysis of mitochondrial and nuclear DNA, combined with morphological studies, has largely resolved their phylogeny.

Recent taxonomic adjustments have refined our understanding of these groups. For instance, the Naucoroidea is now considered monotypic following the separation of the Aphelocheiridae and Potamocoridae into the new superfamily Aphelocheiroidea. Scientists are also investigating the Cibariopectinata, a proposed clade defined by specific structures in the food-sucking pump of advanced bugs. Whether this group is truly monophyletic or synonymous with the Tripartita remains a point of scientific inquiry, highlighting the ongoing nuance in mapping the evolutionary tree of these ancient aquatic insects.

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