We arbitrarily chose two groups of animals that commonly contribute to bioinspired research in materials: butterflies, whose wing characteristics have informed the development of technologies such as electronic displays and solar cells; and spiders, whose silk characteristics have wide applications as a sturdy yet light-weight biomaterial. We searched the WoS database for peer-reviewed research articles using bioinspiration, biomimetics, and butterflies or spiders as key search terms and screened each article for relevant taxonomic information. Specifically, we identified the species that each study was primarily based upon, as well as studies involving multiple focal species. Using a systematic search protocol involving the filtering of irrelevant papers (e.g., articles with no mention of species) and the retrieval of relevant papers from reference lists (e.g., articles using specific terms such as the names of common genera e.g., Morpho for butterflies, Trichonephila or Nephila for spiders), we arrived at 173 research articles for butterflies and 218 for spiders (Supplementary Information).

A similar pattern can be observed in both butterfly and spider inspired research papers: the representation of focal species in this literature is unevenly distributed and focussed on a fraction of the described biodiversity (Figure 1). For example, while the 173 articles that drew inspiration from butterflies included species from 35 genera (Supplementary Table 1), 64% of these species belonged to the family Nymphalidae, and 44% focussed on a single genus, namely Morpho. Clearly, we have explored only the tip of the existing butterfly biodiversity, given the 18,000 formally described species across 125 families (Heppner, 2008; Espeland et al., 2018). A similar pattern emerges for spiders, where 33% of 218 articles focussed on the genus Trichonephila (golden orb-weaving spiders previously a subgenus of Nephila) from a total of 29 represented genera (Supplementary Table 2). In addition, 78% of the articles that drew inspiration from spiders belonged to the superfamily Araneoidea, of which 94% belonged to the family Araneidae (orb-weaving spiders). Nevertheless, the pattern for spiders is perhaps even more alarming than that of butterflies, since spiders are arguably a broader taxonomic group (Araneae), with approximately 49,500 described species from 4033 genera and 113 families (Selden, 2017; World Spider Catalog, 2021). Further, only 12% of butterfly- and 14% of spider-inspired research drew inspiration from multiple focal species.

We arbitrarily chose two design challenges, which have attracted a great deal of bioinspired attention – drag reduction and surface adhesion. Engineers have often looked to nature for ways to improve the hydrodynamic performance of ships and aircrafts; similarly, animals have evolved countless solutions for interfacing with complex natural surfaces, inspiring the development of adhesive tapes and glues. Here, we used the same systematic protocol for research species but instead searched for peer-reviewed research articles with either drag reduction or surface adhesion as key terms. We arrived at 156 papers for drag reduction and 272 papers for surface adhesion (Supplementary Figure 2).

Again, we see a remarkably similar pattern – solutions to both design challenges are primarily drawn from a few model species (Figure 2 and Supplementary Tables 3, 4). In particular, the Tokay gecko (Gecko gecko) is dominant in the surface adhesion literature despite being an unusually large gecko species. We also found that 3% of surface adhesion papers and 10% of drag reduction papers involved species from multiple taxonomic classes, showing that researchers do not usually consider more than one species. This problem of representation was further exacerbated by the lax reporting of taxonomy, especially in the context of popular models. For example, studies involving gecko-based adhesion often simply use the generalised term “gecko” without specifying further details.

The taxonomically narrow approach to research species selection is problematic because significant insights can be overlooked by focusing on only a single genus or family. For example, it was recently discovered that the nanostructures of butterflies facilitates heat dissipation, allowing their thin wings to remain cool despite their large size (Tsai et al., 2020). This insight was made possible by using a multi-species comparative approach to understand processes common to all butterflies, rather than focussing on a single species. Tsai et al. (2020) found key commonalities among the 50 species studied: all had structures that enhanced radiative cooling of the thermally sensitive living parts of the wings (scent patches, scent pads, and wing veins). Differences between species were just as informative: different species used varying combinations of adaptations including cuticle thickness, specialised scale nanostructures, contrasting dorsal and ventral wing coloration, and finely-tuned behavioural reactions to enable temperature to be exquisitely tailored to environmental conditions. Due to the specific combination of traits, butterflies in tropical and temperate environments can bask longer to warm up their bodies while reducing the risk of overheating the wings: whereas butterflies at high latitudes or altitudes can warm up their wings efficiently. This example highlights that comparison of multiple species can reveal how different traits can vary and be combined to suit a wide range of environmental conditions.

Studying multiple species can also highlight the variation in the uses or properties of an adaptation. For example, all spiders produce at least one of seven types of silk that are used in conjunction with different activities, including attracting conspecific mates, forming a cocoon that protects vulnerable eggs, dispersing very considerable distances through ballooning, or capturing prey (Blamires et al., 2017). Yet our knowledge of the properties of spider silk is mostly confined to silks used for foraging, and in particular the dragline silk produced by orb-weaving spiders, the latter informed by a handful of species. Of course, there are excellent reasons for focussing on this type of silk, since it combines two seemingly incompatible properties – strength and elasticity, necessary to absorb the energy of insects arrested at speed. Nevertheless, orb-weaving spiders (Araneidae) are a large and diverse taxonomic group comprising over 3000 species in 177 genera. This taxonomic breadth incorporates remarkable diversity in their foraging ecology, which likely influences the properties of the dragline silk used to support the foraging webs: spiders in the genus Plebs and Leucage build small, delicate and easily broken webs, while the dragline silk that supports the orb-webs of Darwin’s bark spider Caerostris darwini extends tens of meters across rivers (Agnarsson et al., 2010) and is twice as strong as that produced by other orb-weaving spiders (Garb et al., 2019). While differences in dragline silk mechanical properties are also reported among similarly-sized, closely related species (Kerr et al., 2018), the properties of other types of spider silk have been largely ignored. For example, the potential diversity of the tubuliform and aciniform silk used to construct egg cases is poorly understood, but the remarkably rigid, free-standing foraging web of the thomisid spider Saccodomus formivorus also appears to comprise these silks, which could inspire rigid thread designs for tissue engineering (Haynl et al., 2020).

This approach of embracing biodiversity can also be expanded to organisms that live in unusual or hostile habitats. These environments are, by definition, difficult to access and study, and so organisms within them are likely to reveal novel solutions to specific environmental challenges. Notably, this perspective has led to the emergence of “extreme biomimetics”, defined by its focus on bioinspired solutions informed from biologically extreme conditions that are well outside the human comfort zone (Ehrlich, 2017; Petrenko et al., 2019). For example, the skeletal structure of fauna endemic to hydrothermal vents have inspired the study of biopolymers that are thermally stable and high-pressure tolerant under such conditions (Unterlass, 2017). Recent advances in this field have focused on the development of inorganic-organic hybrid materials using chitin or spongin scaffolds exposed to hydrothermal treatments (Ehrlich et al., 2013; Petrenko et al., 2019). This biomaterial fabrication strategy was only made possible by investigating chitin, collagen, and spongin skeletal structures across taxa, eventually settling on sponges (Porifera) as an ideal and renewable source of thermal and pressure tolerant biopolymers (Ehrlich, 2017). Hydrothermal vents are only one example of an extreme environment, and there is obvious value in drawing inspiration from organisms that live in habitats that reflect the extremities of other dimensions, such as oxygen concentration, humidity or cold temperatures. For example, the rapidly growing developments in bioinspired anti-freeze proteins from polar fish and freeze-tolerant insects have promising future biomedical applications (Xiang et al., 2020).

Clearly, there is untapped potential in shifting attention outside of obvious model species, especially as they may not always represent the optimal solution in every context. For example, shark skin is famous for its drag reducing properties, but is by no means the most effective material; other solutions include dolphin skin, penguin-inspired micro-bubbles, and lotus leaf surface structures (Yu et al., 2020). Notably, these species belong to very different phylogenetic groups and their adaptations reflect solutions from different evolutionary perspectives. Similarly, additional insights into surface adhesion may come from insect solutions (Zhou et al., 2014). In short, an optimal bioinspired/biomimetic design can be achieved by understanding, comparing, and even combining insights from nature’s diversity of solutions.

The near infinite functional traits found in nature have been forged by natural selection; this evolutionary design process has quietly progressed for many millions of years. Therefore, by studying living organisms that have survived nature’s optimisation algorithm (Maynard Smith, 1978), we can reap the rewards while skipping our own iterative and time-consuming design processes. This is one of the main appeals of bioinspiration/biomimetics, and biologists are well placed to fully appreciate these systems. However, effective bioinspiration/biomimetics is more complicated than simply selecting a species and replicating the desired adaptation; it can be difficult to identify the most functionally relevant traits to abstract into a design. One solution is to study the evolution of the trait in question using comparative methods, observing whether it appears in related species exhibiting the desired function, and whether it was lost in those without (Adriaens, 2019). Such a comparative approach enables insights into how traits are associated with specific environmental conditions. Again, such an approach requires an appreciation for evolutionary history to take advantage of insights from natural selection (Wolff et al., 2017).

In addition, non-biologists are often unaware of the limitations of natural selection as a design inspiration. While evolution has analogies to the design process, it is not exactly the same and suffers from different constraints. Engineers are often interested in designs that can optimally achieve a single function, however, biological traits are the product of balancing multiple functions and do not represent the objectively optimal solution for one specific function. For example, butterfly wings have inspired the production of structurally coloured materials (Schroeder et al., 2018), yet light manipulation is not their only function. The wings must also be hydrophobic and self-cleaning (Fang et al., 2015), thermally efficient for the animal’s environment (Tsai et al., 2020), and flexible yet durable for flight (Johansson and Henningsson, 2021). Natural selection has favoured a solution that suits all these biological requirements, resulting in a wing structure that is a functional compromise for the animal’s specific environmental conditions. Different species face different environmental challenges and will have varying adaptations to reflect these conditions. This is very relevant to bioinspired/biomimetic design challenges as most synthetic structures or materials also have multiple functional requirements. Identifying biological analogues to these requirements will therefore result in solutions that are better optimised for multiple conditions.

An awareness of phylogenetic constraints is also crucial. For example, while bats have evolved the capacity to fly, it is suggested that their aerodynamic efficiency is inferior to birds due to the phylogenetic constraints associated with their wing design (Muijres et al., 2012). Flexible membranes and elongated digits evolved in bats not because it was necessarily the optimal solution to flight, but because of its evolutionary context (Amador et al., 2019). Engineers also have access to structures and processes that are not readily available to natural selection. For example, the wheel is an energetically efficient invention to facilitate movement, but continuous rotation is rarely possible for animals constrained by musculoskeletal systems (Fish and Beneski, 2014). Biologists are well equipped to navigate these limitations and have the knowledge to properly abstract biological principles whilst avoiding their constraints.

Natural selection provides a diversity of solutions to life’s design challenges; different species can represent distinct or sometimes convergent solutions to similar problems. A focus on single study species provides only one answer to a design challenge, yet the diversity of life shows that there are multiple solutions which can be more or less optimal depending on environmental conditions. Therefore, a focus on the feature rather than species can be more rewarding and provides insights only possible when drawing from the full diversity of life. For example, adaptations for surface adhesion are widespread in the animal kingdom. An awareness of attachment strategies in animals of different sizes can provide insight into issues of scaling with size (Labonte and Federle, 2015), as well as possible solutions to the problem. Interactions between multiple solutions can also be observed when focusing on the feature rather than species. For instance, some animals have both adhesive pads and claws which can potentially be synergistic, or in other cases, redundant (Song et al., 2016; Naylor and Higham, 2019). Understanding the evolutionary contexts behind such interactions can inform the performance and necessity of multiple features in bioinspired/biomimetic designs. Another recent example is the insights drawn from the diversity of insect cuticles. Most insect exoskeletons feature gradual changes in stiffness across the cuticle and analysing this property has directly informed the development of functionally graded materials (Jafarpour et al., 2020). The uncommon, common feature of these examples are that they all draw insights from the diversity of life, rather than focussing on individual species.

In attempts to better appreciate biological diversity for use in art and design, tools such as AskNature have been developed to translate biological information to non-biologists (Deldin and Schuknecht, 2014). These tools serve as rich databases of biological strategies organised by function and can be extremely useful in the initial search for relevant solutions. However, the accessibility of these tools can ironically lead to the perpetuation of popular model species. Such databases do not represent the actual diversity of potential solutions in nature and are by no means an effective replacement for biologists who have expert knowledge on underappreciated systems or strategies (Graeff et al., 2019; Willocx et al., 2020). Therefore, the involvement of biologists continues to be crucial for diverse biological insights in bioinspired and biomimetic designs.

A crucial component of biomimetic design is the abstraction process, as it is often unnecessary to entirely replicate a biological feature (Cutkosky, 2015; Whitesides, 2015). Nevertheless, a nuanced understanding of the biological system is required to abstract a feature effectively. For example, the micro-structure of shark skin needs to be understood in detail before it can be properly simplified into a synthetic riblet (Domel et al., 2018). Incorrectly translating such structures into the final design can result in a potential loss in performance. In addition, a holistic understanding of the system will prevent researchers from becoming too focused on a specific feature in isolation. For example, the Geckskin adhesive technology was developed by abandoning the conventional focus on gecko setae and instead developing a product inspired by the entire gecko foot (Patek, 2014). Here, the research team realised that the setae alone did not explain adhesive performance, but that effective attachment was the outcome of a system of synergistic features at different scales (Imburgia et al., 2019): specifically, the stiff tendons attached to their toepads also played a significant role in effective attachment (King et al., 2014).

It is important to note that gecko-inspired tapes have yet to match the performance of living geckos. Indeed, current gaps in the understanding of biological models remains a major obstacle in biomimetic design. For example, gecko-inspired adhesives have been designed to attach to smooth dry surfaces but are largely ineffective on non-ideal surfaces (Niewiarowski et al., 2016). To further approach the performance of the biological system, it is essential to study questions regarding the ecology of the animal: how are gecko toe pads tuned to specific environmental contexts? How do geckos move across irregular or wet surfaces? How do toe pads vary across species with different environmental challenges? There is considerable morphological variation in geckos, which is linked to habitat (Kulyomina et al., 2019; Norris et al., 2021). These insights from basic biological research are crucial to address current performance gaps and can only be achieved through the involvement of biologists (Higham et al., 2019).

Finally, we emphasise that a bioinspired/biomimetic approach to design is not a one directional relationship. Biologists also stand to gain valuable insights from the process: for example, engineers can provide a different approach toward problem-solving – whilst biologists may only arrive at a conceptual understanding of a trait, in many cases engineers can physically construct and test a structure or property. This direct approach is possible as engineers often have access to resources, technical expertise, and specialist equipment required for the testing and validation of functional hypotheses. Therefore, there is enormous potential for biologists to take advantage of the expertise and resources available to engineers to further explore biological questions in a physical and tangible context (Roberts et al., 2014). For example, biologists often have difficulty studying the functional morphology of extinct species due to the limitations of fossil evidence. Biomimetic tools have allowed for the structures of species such a fossil earwig (Saito et al., 2020) or remora (Gamel et al., 2019) to be replicated to study their evolution and function. In return, these findings provide insights for biomimetic designs, such as the improvement of underwater attachment (remora disc) or folding patterns (earwig wing). A move toward “bioinformation” is both synergistic and mutualistic, allowing biologists and engineers to produce insightful science and useful designs.