Hoverfly mimicry deceives humans

Abstract

It is believed that the resemblance of many hoverflies to stinging hymenopterans is a case of Batesian mimicry, though there is little experimental evidence that it is effective in protecting them from predators. In this study the effectiveness of hoverfly mimicry was investigated for humans by presenting groups of university students and schoolchildren with a questionnaire which included pictures of stinging hymenopterans, mimetic hoverflies and dipteran controls. More people thought that the mimics would sting than either of the control flies, though fewer than those who thought that the mimics' hymenopteran models would sting. This showed that the hoverflies' mimicry worked but was not 100% effective. More people thought that the good mimics would sting than poor mimics which were black and yellow, showing that the reaction was not just due to their warning coloration. Students' identification skills were poor; only 77%, 66% and 50% were able to correctly identify wasps, bumblebees and honeybees, respectively, but even knowledgeable students were confused by mimetic hoverflies. Significantly more of the students who had been stung thought that the Hymenoptera would sting and identified Hymenoptera correctly. Students who thought a hymenopteran would sting were in turn more likely to think that its mimic would sting. This suggests that the mimicry is partly mediated by experience. However, even students who had never been stung showed the same pattern of discrimination as those who had, suggesting that information is also passed on culturally. These results suggest that mimicry is effective and might help hoverflies avoid predation by birds but, as many of the subjects said they would kill a stinging insect, this would actually increase their chances of being killed by humans.

Hierarchical overshadowing of stimuli and its role in mimicry evolution

“…It is well known that humans can be regularly duped by even imperfect mimicry (e.g. see Golding, Ennos, Sullivan, & Edmunds, 2005), while Valkonen and Mappes (2014) proposed that viper mimicry is disadvantageous to smooth snakes when encountering humans, who may kill them after mistaking them for venomous species. Moreover, the primacy of colour in overshadowing reported by Kazemi et al was .…”

An exceptionally high diversity of hoverflies (Syrphidae) in the food of the reed warbler (Acrocephalus scirpaceus)

“…Moreover, birds may pay more attention to other cues (prey traits) than colour patterns (e.g., qualities of flight motion). Thus, a human observer may mistakenly judge a hoverfly as a mimic of a hymenopteran insect (e.g., Golding et al, 2005) when in fact there is no mimicry in the eye of the relevant beholder -the avian predator (for detailed discussion of other explanations for the maintenance of poor Batesian mimicry see Edmunds, 2000;Ruxton et al, 2004;Grim, 2005).…”

Which traits do observers use to distinguish Batesian mimics from their models?

“…The "carry-over" we observed emphasizes that differences in early learning experiences (which in the wild can be varied and unpredictable) can have persistent effects on later behavior. Several previous studies have adopted a similar approach of using humans as surrogate predators to judge the accuracy of mimics, and show the utility of using human test subjects in enabling a large sample size (Golding et al 2005b;Penney et al 2012;Sherratt et al 2015). Of course, results from human trials can only be applied to real mimetic systems with a degree of caution, although their results tally well with other studies that have used avian predators (Dittrich et al 1993;Kazemi et al 2014).…”

“…Past studies that have used humans as predators (Golding et al 2005b;Sherratt et al 2015) have (to varying degrees) used the somewhat unrealistic scenario of the subjects being given time to inspect the images at their leisure, and in addition, Penney et al (2012) presented large, high-resolution images. The present work used a short presentation of a low resolution image in order to best resemble the situation in which a predator must make a quick decision based on an insect viewed from a distance, with any hesitation allowing the prey a chance to escape (Chittka and Osorio 2007;Abbott and Sherratt 2013).…”

“…Humans provide a useful model "predator", with fewer ethical and practical constraints, and experimental games in which humans "forage" for prey have previously generated large datasets to explore hypotheses about mimicry (Golding et al 2005b;McGuire et al 2006;Sherratt et al 2015;Morris and Reader, in review). Humans have been shown to make judgments about mimetic accuracy similar to those of birds, which are thought to provide the main selective pressure for mimicry in hoverflies (Dittrich et al 1993;Penney et al 2012;Sherratt et al 2015).…”