Entomological collections face significant challenges in storing and preserving dissected structures of insects (especially the most delicate and tiny ones). For pinned specimens, few alternatives are available to keep dissected parts along with their source specimens, with pinnable microvials commonly used. However, world suppliers for these special microvials are scarce and their cost may reasonably impact the budget of less wealthy institutions. To provide a low-cost alternative, we designed a reliable entomological dissection microvial, based on materials easily found in most local office and laboratory equipment suppliers. Our microvials are based on two main items, Polypropylene (PP) microcentrifuge tubes and Ethylene Vinyl Acetate (EVA) hot-melt glue. Their manufacturing process is very simple and is described and illustrated in detail. The proposed microvials tend to have good ability for archiving, since the materials used for their main parts (PP and EVA) show good chemical adhesion and PP microcentrifuge tubes can safely contain most common preserving solutions for an indefinite time. Their endurance was tested under normal use conditions in our collection for the past five years and materials showed no degradation. Moreover, all components are classified as non-toxic and are safe for manipulation, storage and disposal by any educational or research facility. Finally, they fit into the category of sustainable solutions once they are long-lasting, reusable and can be manufactured from used microvials that would be discharged.

Alternative methods, entomological collections, genitalia vials, microtubes, preserving, storage

Zoological collections hold ex situ biological material of all kinds of animals. Their main purpose is to keep and guard faunal representatives and data for biodiversity knowledge and for scientific studies in a vast range of areas like public health (e.g. Hoffmaster et al. (2002)), agriculture (e.g. Davies et al. (1999)) and climate change (e.g. Parmesan et al. (1999)) (Suarez and Tsutsui 2003; Pyke and Ehrlich 2010; Paknia and Koch 2015). Zootaxonomy and zoosystematics are particularly dependent on zoological collections as sources of data on species morphology, diversity, distribution and for acquiring biological samples (Suarez and Tsutsui 2003; Pyke and Ehrlich 2010). Therefore, proper storage and maintenance of specimens deposited in collections are crucial for preserving biological and historical heritage of living beings throughout time (Engel et al. 2021).

As the most diverse group of organisms on Earth, insects are unmatchable in diversity of species, morphological traits and habits (Zhang 2011; Storck 2018); thus, entomological research often relies on surveying specimens from collections aiming for a wider and deeper look on a given taxon (Camargo et al. 2015). The vast majority of the entomological collections are maintained mainly through public funding, due the high costs involved and their non-profit purpose (Britz et al. 2020).

However, leaving collections maintenance programmes at the mercy of political-economical decisions may be problematic, especially in Global South countries which struggle frequently to maintain long term policies devoted to non-basic needs (Agenda 2030 2015; Magalhães 2024). Add to that the tariff and exchange rate issues when purchasing imported laboratorial supplies (most from EU and US) and you may rapidly face an unfeasible scenario for less wealthy countries and their institutions, to keep well-maintained biological collections (Quintans-Júnior et al. 2020). Yet, many countries considered as “megadiverse” fall into the aforementioned category, which amplifies issues related to the lack of adequate structure and resources for them to safeguard properly the vast entomological material coming from their native areas (Paknia et al. 2015).

Preserving the most delicate diagnostic structures of insects, such as mouthparts, appendages and genitalia, poses a challenge to entomological collections. If properly preserved, these parts can last for centuries, safeguarding important biological information. In the case of preserving insect genitalia, microvials with glycerine are widely used as an alternative to mounting on permanent slides or simply gluing them to small paper boards, as it allows for further manipulation of the preserved parts (Young and Beirne 1958; Gurney et al. 1964).

However, finding vials suitable for this purpose is not an easy task, as they need to be small (around 1.0 to 2.0 centimetres) and attachable to the specimen’s pin from which it was extracted. With this issue in mind, Gurney et al. (1964) presented all existing solutions and techniques available at the time involved in preserving insect genitalia in microvials. Later, Deitz (1979) proposed the use of very small glass vials with cork stoppers, despite Gurney et al. (1964) having already condemned this practice, as the cork tends to dry out and crack. Aiming to solve that, van Doesburg (1980) suggested manufacturing PVC tubes sealed with a silicone stopper derived from medical supplies, resulting in the first self-manufactured low-cost microvial. However, the resulting tube was too big for smaller specimens and acquiring the needed medical supplies is not practical for a typical entomologist. So far, all commercial alternatives for genitalia microvials are variations of these techniques and are still widely used in collections worldwide.

Although simple in design and not demanding expensive materials for production, these tubes are manufactured for a very small niche market and have a considerably high final price. We surveyed the purchase costs for entomological microvials from online stores of seven worldwide suppliers and reached an average cost of 27.5 US Dollars per 100 units (Table 1). The value may not seem absurd at first glance, but when scaled up to purchases around tens of thousands of units (ordinary numbers of pinned specimens preserved in many entomological collections), it can impact the budget of collections. Additionally, all these suppliers are physically located in Europe (with one in Australia) (Table 1) which makes the acquisition even harder for collections located in the Global South.

Faced with these challenges on a daily basis, our staff at the Entomological Collection of the Federal University of Tocantins (CEUFT) is constantly looking for affordable, but adequate, solutions for preserving and maintaining specimens. Over the past five years, we have successfully used self-manufactured dissection microvials for pinned specimens, which remain in very good condition. Taking into account that similar resource limitations affect emerging collections worldwide, we present here a step-by-step guide for producing a low-cost entomological microvial for storage of the genitalia and other dissected structures, using materials readily available from local suppliers anywhere in the world.

Authors thank UFT for the support and the Brazilian Innovation Agency (FINEP) project “Análise e Mapeamento da Biodiversidade e Recursos Hídricos do Estado do Tocantins” (process number 01.18.0077.00) for financing equipment and infrastructure. JCG thanks the Coordenação de Aperfeiçoamento de pessoal de Nível Superior (CAPES) and the Fundação de Amparo à Pesquisa do Estado do Tocantins (FAPT) for the scholarship grant (n. 88887.6292119/2021-00). TKK thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for the scholarship grant (n. 310214/2021-1).