Research Article |
Corresponding author: Max Caspers ( max.caspers@naturalis.nl ) Academic editor: Maria Heikkilä
© 2019 Max Caspers, Luc Willemse, Eulàlia Gassó Miracle, Erik J. van Nieukerken.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Caspers M, Willemse L, Miracle EG, van Nieukerken EJ (2019) Butterflies in bags: permanent storage of Lepidoptera in glassine envelopes. Nota Lepidopterologica 42(1): 1-16. https://doi.org/10.3897/nl.42.28654
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In terms of amateurs and professionals studying and collecting insects, Lepidoptera represent one of the most popular groups. It is this popularity, in combination with wings being routinely spread during mounting, which results in Lepidoptera often taking up the largest number of drawers and space in entomological collections. As resources grow increasingly scarce in natural history museums, any process that results in more efficient use of resources is a welcome addition to collection management practices. Therefore, we propose an alternative method to process papered Lepidoptera: a workflow to digitize (imaging and data registration) papered specimens and to store them (semi)permanently, still unmounted, in glassine envelopes. The mounting of specimens will be limited to those for which it is considered essential. The entire workflow of digitization and repacking can be carried out by non-expert volunteers. By releasing data and images on the internet, taxonomic experts worldwide can assist with identifications. This method was tested for Papilionidae. Results suggest that the workflow and permanent storage in glassine envelopes described here can be applied to most groups of Lepidoptera.
Butterflies and moths are amongst the organisms that have always been very popular with collectors and scientists. They also are among the most difficult invertebrates to prepare: it takes skill, time and proper tools to expertly set specimens. Hence, most collectors who are away from home do not prepare specimens straight away but store them temporarily, either pinned but not spread, or stored flat in boxes or opaque paper envelopes. Papering traditionally consists of placing specimens with the wings folded upwards in triangles of paper, or in small rectangular envelopes of glassine paper (
Over time, most natural history museums have amassed large collections of papered specimens, originating from private collectors and expeditions of these museums, and most of these have never been properly prepared. Due to lack of resources, many of these collections have been left undisturbed, often for decades, and curators are struggling how to make this material accessible for research.
In 2015 the number of papered Lepidoptera in the collection of Naturalis Biodiversity Center, Leiden, the Netherlands was estimated to consist of roughly 500,000 specimens, some being as old as 80 years. A substantial part of the backlog (>200,000 specimens) consisted of Lepidoptera collected by J.M.A. van Groenendael, a Dutch physician working in the former Dutch East Indies between 1931 and 1954 (
Though specimens in papered envelopes potentially contain a wealth of information for research, their current storage method seriously hinders study. In practice this means that such collections have been neglected for decades, with only an occasional search for interesting specimens. This involves a high risk for damage and sometimes results in damaged legs, antennae or even wings. Processing this number of Lepidoptera following current practice, namely pinning and spreading the specimens, would take up roughly 7500 drawers, not to mention the personnel it takes. As space, time and money are resources that have been growing increasingly scarce for natural history museums in the past decade (
For collections of Odonata (dragonflies and damselflies), rectangular 3×5 inch index cards and transparent envelopes of film were proposed some decades ago as a permanent storage solution for unmounted specimens (
In order to properly process the collection of 500,000 papered butterflies and moths at Naturalis, repacking should be combined with a digitization workflow. Additionally, to potentially reduce costs, non-expert volunteers should be able to carry out this workflow. A pilot project was carried out in 2016 to put this to the test, funded by the Van Groenendael-Krijger Foundation. During this project a workflow was developed to repack and digitize large collections of unmounted Lepidoptera. This is an approach that differs from the traditional practice of mounting Lepidoptera in a way that is less time, space and money consuming, while ensuring optimal accessibility to the collection, both physical and digital. In this paper a workflow for digitizing and permanently storing unmounted Lepidoptera is presented, that resulted from the 2016 pilot. The digitization and repacking of all papered Lepidoptera is currently (June 2018) still going on. It is estimated that another ten years are required to completely deal with the backlog of papered specimens. We will continuously seek to refine the workflow and storage method, and are happy to confer with prospective users.
Throughout the 18th and 19th centuries, collectors devised different methods to preserve delicate butterflies and moths. The apothecary James Petiver (1663–1718), for example, preserved his butterflies dried, pressed and glued in books “after the same manner you do the Plants” (
Regarding the methods to spread Lepidoptera, the artist Benjamin Wilkes (died c. 1749) was one of the first to write down instructions for setting butterflies and moths in his “Directions for Making a Collection” (
More recently, new preservation and storage techniques have been developed for fresh or recently acquired material in order to facilitate morphological and molecular research, such as fluid preservation and freezing of the specimen bodies, while the wings are saved in clear plastic coin holders (see for example
In order to maximize the use of storage space, curators of large collections often fill insect drawers as much as possible by letting the wings of the butterflies overlap, or in case of moths, by not spreading some of them. This has obvious disadvantages. In the case of overlapping wings, it results in overcrowded drawers, with greater risk of damage for the specimens. Unmounted moths are, on the other hand, difficult to examine. Pinning moths without spreading, that is, with their wings close to the abdomen, however, may be more efficient than papering.
For specimens belonging to easily identifiable species, often only collected to serve as a faunistic voucher, there is no direct need for mounting in order to obtain the necessary information. This means that for long series of specimens with similar label data, the default storing method could be unmounted in envelopes in order to save space. Only when other kinds of research require a traditionally mounted specimen, it is necessary to select the specimens and spread them.
For DNA studies, papered specimens may yield even better results, as they have never been relaxed. Relaxing requires exposure to moisture and therefore may be detrimental to DNA quality (see for example
Here we describe a three-phase workflow developed to tackle the enormous collection of 500,000 papered Lepidoptera at Naturalis Biodiversity Center. Central to this workflow is the idea that Lepidoptera will be permanently stored in glassine envelopes, still unmounted, in contrast to mounting as the traditional method of storage. In the first phase of the workflow non-expert volunteers repack and digitize the papered Lepidoptera, while taxonomic experts take care of the identification in the second phase. The post-processing in the third phase is the responsibility of collection managers. Step by step we will treat the three sequential phases of this workflow: repacking and digitization, identification and post processing.
To test the designed workflow during the pilot in 2016, a selection of envelopes was made that comprised the papered Papilionidae (swallowtails) collected by J.M.A. van Groenendael in Java, Indonesia. This family of butterflies was chosen for several reasons. In the first place, it is one of the smallest families of butterflies, comprising around 180 species in the Oriental region (
Deciding which specimens should be processed first is primarily dependent on ongoing research. In the absence of ongoing research, prioritizing the papered Lepidoptera is based on taxonomy, so the project only needs to depend on one expert at a time. Therefore, once the Papilionidae are fully processed, the rest of the papered Lepidoptera collection will be processed by family during the expected 12 year life span of the project.
To digitize and store specimen metadata for each swallowtail together with their image, the Collection Registration System (CRS) in use by Naturalis was chosen. CRS was developed during the FES Collection Digitization project (
Phase 1, which does not require in-depth knowledge, is carried out by volunteers in order to reduce costs. A team of volunteers was recruited sufficient to occupy three workstations five days a week. As most volunteers are available for one day per week the team includes some 20 persons to accommodate for illnesses and holidays.
Step 1: Pre-processing by project coordinator
1. All information available on storage unit level, such as collecting date and location or collection name, is registered in the Naturalis Collection Registration System (CRS) as first basic information for further individual registrations.
2. A stock of blank 3×5 inch index cards is printed, which contain a unique data matrix and registration number. These labels are printed on thick, 100% cotton, acid free ledger paper to ensure sustainable storage. The registration numbers are consecutive to improve usability. Labels are subsequently cut to perfectly fit the glassine envelopes. This provides support and protection for the specimen in the glassine envelope.
The result is a prepared drawer of papered Lepidoptera with a supply of unique 3×5 inch cards (Fig.
Step 2: Handling by volunteers (Fig.
1. The next index card as well as a random papered butterfly or moth is taken from the prepared drawer. The information written on its envelope, most commonly collecting locality and date, is registered into the CRS database.
2. The specimen is taken out of its original envelope and is imaged together with the original envelope and the newly printed index card (Fig.
3. The label is inserted into a glassine envelope, after which the specimen carefully follows. The glassine envelopes are finally placed in numerical order by their registration code, in small cardboard boxes that fit in tailor made drawers (Fig.
Step 3: Completion by the project coordinator
After volunteers have registered, imaged and stored the specimens in glassine envelopes, the project coordinator makes sure that the quality of the data is up to standard and that the digital and physical collections are properly organised. This includes a weekly quality control of the data in the generated specimen records, renaming and linking the produced images to the corresponding specimen records and ensuring the specimens and drawers are stored properly.
The entire process of phase 1 is schematically represented by a flowchart (Fig.
The images taken during step 2 of phase 1 are sent by the project coordinator to a taxonomic specialist in the respective Lepidoptera family. Using the images, the specialist identifies specimens to the lowest taxonomic level possible and registers the taxonomic information in an external file. During this process, the specialist can mark the specimen for mounting and/or DNA-sampling when deemed necessary, i.e. when identification using solely the ventral view of the wings is not possible or the specimen is very rare in collections. The project coordinator imports the specialist’s identifications from the external file into the CRS database so they correspond with the specimens and accompanying records.
For the Naturalis collection of papered Lepidoptera, it is practically impossible to determine whether all specimens in a drawer selected for repacking and digitization belong to a certain family. The collection is only roughly sorted by family and the envelopes are usually opaque. Since the volunteers are not expected to identify Lepidoptera, all specimens from prioritized drawers are processed even though they might belong to another family. In the case of the 2016 pilot, the Papilionidae expert identified the non-Papilionidae to at least family level so these can later be easily redirected to their respective expert.
At the time of writing, the project is experimenting with deep learning image recognition to reduce the time a specialist has to put in identifying specimens of common species (
The collection of Lepidoptera resulting from the first two phases, as described above, is ordered numerically by their registration code. On the other hand, the Naturalis collections of mounted Lepidoptera and papered Odonata are ordered taxonomically. A logical next step would be to reorder the butterflies in envelopes to fit this system. However, as the specimens are easily traced individually by their identification numbers, there is no direct necessity to reorder and handle all specimens again. If there is need for a taxonomically ordered collection of papered butterflies in the future, a re-curation workflow will be set up.
A more pressing issue at the moment is dealing with the specimens that are marked by the expert to be mounted or DNA sampled, for example, when identification was not possible using only the photograph. These specimens will be extracted from the papered collection and professionally mounted for further examination.
The described workflow yields a thoroughly curated collection, both physically and digitally. The physical collection of unmounted Lepidoptera in glassine envelopes is archived sustainably and is easily accessible due to being ordered numerically. The digital collection comprises a photograph, an identification and in most cases a collection date and locality information for each individual specimen. Notably, the new workflow is especially efficient when compared to the traditional practice of mounting. During the 2016 pilot the team of volunteers digitized a total of 16,440 specimens, mostly Papilionidae, none of which required mounting for further study. The gains in time, space and costs are discussed below. In the workflow here presented, the gains in resources are by and large dependent on the percentage that still requires mounting after digitization. Because Papilionidae in this respect are not representative for all Lepidoptera, several situations that depict varying levels of mounting requirements are included in the calculations as well.
In Table
Time required to handle and digitize 16,440 specimens of Papilionidae in four scenarios, compared to the traditional practice of direct mounting. Scenario 1 corresponds with the results of the 2016 pilot.
16,440 specimens of Papilionidae | Proposed method - scenario 1 | Proposed method - scenario 2 | Proposed method - scenario 3 | Proposed method - scenario 4 | Traditional practice - direct mounting |
---|---|---|---|---|---|
% that requires mounting | 0 | 25 | 75 | 100 | 100 |
Handling time (days) | |||||
a. envelopes (40 ex./day) | 411 | 411 | 411 | 411 | |
b. mounting* (20 ex./day) | 0 | 206 | 617 | 822 | 822 |
Total handling time (days) | 411 | 617 | 1028 | 1233 | 822 |
In Table
Drawers required to store 16,440 specimens of Papilionidae in four scenarios, compared to the traditional practice of direct mounting. Scenario 1 corresponds with the results of the 2016 pilot.
16,440 specimens of Papilionidae | Proposed method - scenario 1 | Proposed method - scenario 2 | Proposed method - scenario 3 | Proposed method - scenario 4 | Traditional practice - direct mounting |
---|---|---|---|---|---|
% that requires mounting | 0 | 25 | 75 | 100 | 100 |
Number of drawers required | |||||
a. envelopes (350 ex./drawer) | 47 | 36 | 12 | 0 | 0 |
b. mounting (50 ex./drawer) | 0 | 83 | 247 | 329 | 329 |
Total number of drawers required | 47 | 119 | 259 | 329 | 329 |
In Table
Costs required to handle and digitize 16,440 specimens of Papilionidae in four scenarios, compared to the traditional practice of mounting. Scenario 1 corresponds with the results of the 2016 pilot.
16,440 specimens of Papilionidae | Proposed method - scenario 1 | Proposed method - scenario 2 | Proposed method - scenario 3 | Proposed method - scenario 4 | Traditional practice - direct mounting |
% that requires mounting | 0 | 25 | 75 | 100 | 100 |
Material costs involved* (€) | 6753 | 10277 | 16376 | 19426 | 18100 |
A new workflow is presented for processing papered Lepidoptera specimens as an alternative to mounting all individuals. This workflow entails digitizing the specimens and repacking them, still unmounted. Mounting is limited to those specimens that otherwise cannot be identified or are special or rare. Results indicate that the efficiency of this workflow depends on the number of specimens that still require mounting after processing. For Papilionidae, due to their size and relative ease of identification, saving resources when applying the new workflow is evident. For other groups, i.e. most moth families, this workflow most likely is less efficient when aiming at identifying all specimens to species level.
Nevertheless, even if identification of unmounted material is only possible to a higher taxonomic level (i.e. family or subfamily), applying this workflow is still advantageous. A large number of papered Lepidoptera will be individually processed and stored in an acid-free durable environment available for further study. Not only is a high level (family or subfamily) identification already an enormous improvement, the locality and date for each specimen becomes digitally available as well. This will facilitate research and improve selection of specimens to be mounted for further study. The photographs are disseminated online and sent to experts for identification.
When faced with the decision whether to apply this new method to process a collection of papered Lepidoptera or mount all specimens at once, being able to estimate the percentage that will require mounting is a welcome addition. So far this has proved to be quite difficult considering the historical nature of the collection with limited documentation and most envelopes being opaque. Perhaps knowledge about the collector might help in indicating what kind of Lepidoptera are to be expected, but in general the means of assessing beforehand the probable gains in time, space and cost requires further scrutiny.
Finally, future automated identification tools for unmounted Lepidoptera that recognize shape and colour patterns of the wings would perfectly fit into the workflow presented here (
The original envelopes are not stored physically with the specimens, except for ones with exceptional historical information or where the source data is very hard to read and keeping the original envelope might provide beneficial. The method of digitization results in images and verbatim transcriptions of the source data on the original envelopes. This allows the source data to always be digitally accessible for inspection when there is doubt about the validity of the transcribed or interpreted data. A representative selection of the original envelopes is kept separately in our archive because of their historical value. Instead of disposing the rest of the original envelopes, alternative uses such as outreach are being explored.
Eventually a papered collection of taxonomically arranged Lepidoptera may form an important supplementary collection next to the traditional collection of mounted specimens. It is already common practice in some laboratories to keep voucher specimen used for tissue extraction for DNA in envelopes (N. Wahlberg, personal communication;
The authors would like to thank the Van Groenendael-Krijger Foundation for their collaboration and significant financial support. The Uyttenboogaart-Eliasen Foundation is gratefully acknowledged for financially supporting the presentation of the project at conferences. We also thank the taxonomic specialists Jan Moonen (Southeast Asian Papilionidae) and Stefan Schröder (Lycaenidae) as well as the dedicated and passionate group of volunteers Els Baalbergen, Michiel Balvers, Jasper Boldingh, Luisa de Bruin, Atie Grimbergen, Herman Hillebrand, Maja de Keijzer, Annemarie Kingmans, Maarten Koster, Renate Kramer, Miriam Langeveld, Ad Littel, Cindy Manshanden, Patrick Ouwehand, Marlous Pigeaud, Jorg Schagen, Frank Stapert, Caroline Stroeks, Patrick Verhoeks, Jaël Visser and Taco van Welzenis. Rienk de Jong and Rob de Vos are acknowledged for support and advice on practical and scientific matters. Without all these people this project would not have been possible. Geoff Martin is acknowledged for his critical remarks that helped to improve the final version of the manuscript.
Permanent storage of Lepidoptera in glassine envelopes
Data type: product information