First published: 28 October 2025.
A recent review article in Physiological Entomology posits that brain structures associated with associative learning in beetles are very flexible, due to diverse adaptive pressures and lifestyles.
In recent years, the ability of associative learning and related brain structures has become one of the most attractive topics in physiological research on insects. It is well-documented that the ability to learn is not an exclusive privilege of animals with large brains. Associative learning represents a fundamental adaptation mechanism, enabling animals to respond to dynamic and diverse environments. Learning is one of the fundamental forms of cognition, and studying it across the widest possible spectrum of species is crucial for the comparative analysis of cognitive functions.
Despite their relatively short lifespan and relatively small brains (compared to vertebrates), insects are able to learn moments essential for survival, remember them, and adjust their behaviour accordingly. Thus far, the greatest attention has been paid to the main model organisms, such as the fruit fly, honeybee, cricket, migratory locust, and American cockroach.
The study, authored by Jiří Dvořáček and Dalibor Kodrík, focuses on beetles (Coleoptera) and their brain prerequisites for associative learning – the structure called the mushroom body. Beetles are not yet considered typical laboratory organisms, and the cognitive abilities of beetles remain largely on the periphery of scientific attention. And yet, their activity often has significant impacts on the human economy and other activities, and they represent one of the most interesting groups of insects for the general public. The beetles are the largest group by species, not only of insects, but of animals in general; over 380,000 species have been described so far, and it is likely that many more species are still waiting to be described. During their long evolution, they have diversified into an extraordinary ecological and morphological diversity and have occupied almost all niches on this planet aside from the marine world. At the same time, each group of beetles and each individual species is adapted to living conditions with a unique physiological arrangement. It is precisely their varied lifestyles that make beetles an exceptionally interesting group for neurobiological research.
The authors present beetles as an exceptional model system for studying the evolution of higher brain centres and for understanding the relationship between the evolution of cognitive functions and the ecology of specific species. They also elucidate the general principles underlying cognitive functions.
“The flexibility of beetle brain structures and their adaptation to the ecological needs of a particular species – often despite the brain equipment of a related species – is fascinating. Species have traditionally been distinguished from each other by selected morphological characters.
To put it with a slight exaggeration: if brain structure were chosen as such a morphological character, a completely different taxonomy would result.”
– Jiří Dvořáček
The vast diversity of the mushroom bodies corresponds to the beetles’ high ecological diversity. The morphological variability of the mushroom body confirms the fascinating fact that there is no single “correct” path to brain evolution. Within individual families, they find many evolutionarily and genetically closely related species that exhibit vastly different ways of life, each with specific brain adaptations “tailored” to the needs of the species in their respective environments.
Some species of beetles have relatively simple mushroom body structures, similar to those of flies (Diptera); however, in other beetle species or groups with similar ecologies (even across families), morphologically complex mushroom bodies can be found similar to those of Hymenoptera, whose mushroom bodies are highly complex in structure and equipped with intricate neural networks. Thus, on the one hand, beetles offer a wide range of processes for doubling mushroom body structures, increasing their synaptic surface, increasing the number of neurons, and lobe compartmentalisation—which allows for the creation of a modular structure and local circuitry as conditions for increased computing capacity—and on the other hand, they also show some simplifications.
When comparing the evolution of the brain in individual families, one feature stands out: the great evolutionary plasticity of the mushroom body structure, even among closely related species. Within a family, a particular mushroom body arrangement usually dominates, but species are regularly found that have conspicuously more (or less) evolved mushroom bodies compared to those of their close relatives. Taxa across evolutionary ranks exhibit similar mushroom body structures when subjected to comparable adaptive pressures and lifestyles.
The evolutionary trajectory of an entire group of beetles is primarily shaped by the ecological requirements of individual species, particularly by their specific information processing needs driven by unique living conditions. However, these adaptations are inherently constrained by factors such as body structure and developmental limitations.
“The study of non-traditional animal models, such as insects, often results in exciting insights that can help us comprehend broader biological problems or be employed in practice in the future.”
– Dalibor Kodrík
The same activity may impose vastly different information processing demands depending on the organism’s somatic adaptations and the stability and complexity of its environment. Therefore, it is necessary to study brain functions not in isolation, but as an inseparable part of the complex relationships between the brain, body structure, and environmental context. Beetles may be ideal for comparative studies on this continuum. It is particularly intriguing that these relationships and the selection pressures driving structural changes in insect brains are likely similar to those shaping the brains of vertebrates, including humans.
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