Precision glycerine jelly swab for removing pollen from small and fragile insect specimens

Historical datasets can establish a critical baseline of plant-animal interactions for understanding contemporary interactions in the context of global change. Pollen is often incidentally preserved on animals in natural history collections. Techniques for removing pollen from insects have largely been developed for fresh insect specimens or historical specimens with large amounts of pollen on specialised structures. However, many key pollinating insects do not have these specialised structures and thus, there is a need for a method to extract pollen from these small, and fragile insects. Here, we propose a precision glycerine jelly swab tool to allow for the precise removal of pollen from old, small, and fragile insect specimens. We use this tool to remove pollen from five families of insects collected in the late 1970s. Additionally, we compare our method with four previously published techniques for removing pollen from pinned contemporary specimens. We show the functionality of the precision glycerine jelly swab for removing small quantities of pollen across insect families. We found that across the five methods, all removed pollen; yet, it was clear that some are better suited for fragile specimens. In particular, the traditional glycerine jelly swab and the precision glycerine jelly swabs both performed well for removing pollen from bee faces. The shaking wash resulted in specimen fracture and residue left behind, the ethanol rinses left setae matted, and the glycerol swabbing left residue on the specimen. Additionally, we present photographs documenting the effects of these methods on pinned honey bee specimens. The precision glycerine jelly swab opens up opportunities to sample pollen from a variety of insects in natural history collections. These pollen samples can be incorporated into downstream analyses for pollen identification either via microscopy or DNA sequencing, and the resulting plant-insect interaction data can establish historical baselines for contemporary comparison. Beyond our application of this method to pollen on insects, this precision glycerine jelly swab tool could be used to explore pollen placement specialisation or to sample bryophyte, fungal, and tree fern spores dispersing on animals.历史标本数据集可为阐明全球变化背景下的当代动植物相互作用（plant-animal interactions）建立关键基准。花粉常偶然留存于自然历史馆藏（natural history collections）的动物标本体表。此前用于从昆虫身上提取花粉的技术，大多是针对新鲜昆虫标本，或是在特化结构（specialised structures）上附着有大量花粉的历史标本开发的。然而，多数关键传粉昆虫并不具备这类特化结构，因此亟需开发可从这类小型脆弱昆虫标本上提取花粉的方法。本研究提出一种精密甘油明胶拭子工具（precision glycerine jelly swab tool），可精准去除老旧、小型且脆弱的昆虫标本表面附着的花粉。我们使用该工具从采集于20世纪70年代末的5个昆虫科的标本中提取了花粉。此外，我们将本方法与4种已发表的、用于从针插式当代昆虫标本上提取花粉的技术进行了对比。结果表明，精密甘油明胶拭子可有效从多个昆虫科的标本上提取少量花粉。研究发现，5种方法均能提取花粉，但显然部分方法更适用于脆弱标本。具体而言，传统甘油明胶拭子与本研究提出的精密甘油明胶拭子均能有效从蜜蜂体表提取花粉。振荡清洗法会导致标本断裂并残留附着物；乙醇冲洗法会使昆虫刚毛（setae）黏结成团；甘油拭擦法则会在标本表面留下残留物质。此外，我们还提供了照片，记录了这些方法对针插蜜蜂标本造成的影响。精密甘油明胶拭子工具为从自然历史馆藏的各类昆虫标本上采集花粉提供了可行途径。所获花粉样本可通过显微镜观察或DNA测序（DNA sequencing）用于后续的花粉鉴定分析，由此得到的动植物相互作用数据可为当代动植物相互作用研究建立历史基准。除了用于提取昆虫体表的花粉外，该精密甘油明胶拭子工具还可用于探究花粉附着特化模式，或是采集附着在动物体表的苔藓植物、真菌以及树蕨孢子。