An Easy Method to Sample Headspace Pheromones in the Field

Signal evolution is complex as it is subject to multiple, often antagonistic selection pressures and the result is expected to be a compromise between getting the signal to the desired recipient at minimal costs and avoiding or at least minimising reception by an unwanted audience. In comparison to other modalities, we know very little about chemical signals, even though they are particularly widespread across many taxa, including spiders. Spiders use volatile chemicals to attract prey and mating partners but are predominantly studied in the laboratory. This leaves a gap in our knowledge concerning the natural context and environment for signalling in this large arthropod group. The chemical nature of the sex‐pheromone is known for 12 spider species, including the wasp‐spider Argiope bruennichi . Recent laboratory experiments with this species have shown that pheromone production is condition dependent and that females invest strategically into signalling. One consistent result from the lab was that freshly matured females do not emit pheromones for at least 3 days. However, in the field many freshly matured females have one or more guarding males in their webs, putting our laboratory results into question. To solve this incongruity, a method for sampling under field conditions was required. Here we present a simple method that we developed to sample pheromone emission of an orb‐web spider in the field.