A fast and easy mass sampling method for social bee crop content

Abstract

Honey bees (Apis mellifera) are capable of foraging over large distances around their nest and can thus serve as ideal bioindicators for various research questions. While foraging for nectar, they collect a variety of pollutants such as environmental toxins and agrochemicals, which can be traced in their digestive tract. Likewise, naturally occurring compounds in a bees crop content (e.g., different sugars and pollen grains) can be analyzed to assess the foraging preferences of bees or to study the species composition of flowering plants in the respective environment. Regardless of the research question, a precise, reproducible, and efficient method for examining pollinators crop contents is needed to fully exploit the honey bees potential as a bioindicator. Existing methods are often insufficiently precise with respect to the recovered volume and content, too time-consuming or lack the opportunity to store samples flexibly. Consequently, they do not meet the requirements of large-scale sampling commonly needed in scientific field work. We present a novel, rapid and scalable method for fast and easy mass sampling of honey bee crop contents which holds potential for adaptation to other pollinator taxa such as bumblebees. With this method individuals can be collected in the field and stored prior to sample processing. Crop contents can be obtained later on by centrifuging the entire individual, thereby decoupling sample collection from further analysis. Afterwards, insect samples and extracted fluids can be stored again, enabling subsequent analysis in an efficient and time-saving manner. We demonstrate that crop contents of previously fed animals can be obtained precisely in terms of both volume and composition and present an example of application in honey bee foraging ecology as a proof of concept.