Is the hibiscus harlequin bug aposematic? The importance of testing multiple predators

Abstract

Aposematism involves predators learning conspicuous signals of defended prey. However, prey species utilize a wide range of chemical (or physical) defenses, which are not likely to be equally aversive to all predators. Aposematism may therefore only be effective against a physiologically sensitive subset of potential predators, and this can only be identified through behavioral testing. We studied the emerging model organism Tectocoris diophthalmus (Heteroptera: Scutelleridae), an aposematically colored but weakly defended shieldback stinkbug, to test the efficacy of its defenses against a suite of predator types. We predicted the bugs' defenses would be ineffectual against both experienced and naïve birds but aversive to predaceous insects. Surprisingly, the opposite pattern was found. Both habituated wild passerines and naïve chickens avoided the bugs, the chickens after only one or two encounters. To avian predators, T. diophthalmus is aposematic. However, praying mantids showed no repellency, aversion, or toxicity associated with adult or juvenile bugs after multiple trials. Comparison with prior studies on mantids using bugs with chemically similar but more concentrated defenses underscores the importance of dose in addition to chemical identity in the efficacy of chemical defenses. Our results also emphasize the importance of behavioral testing with multiple ecologically relevant predators to understand selective pressures shaping aposematic signals and chemical defenses.

Does it Pay to Care?: Exploring the Costs and Benefits of Parental Care in the Hibiscus Harlequin BugTectocoris diophthalmus(Heteroptera: Scutelleridae)

“…) and aposematic (Fabricant et al. ), which renders them unpalatable to avian predators (Fabricant & Smith ), which may reduce the potential predation risk associated with guarding. Furthermore, it is unusual to see unguarded egg clutches in the field at any time of year (R. Giffney, pers.…”

Methods for independently manipulating palatability and color in small insect prey

“…Yet, there are also remarkable differences in the responses of some of these predators. For example, jumping spiders have limited ability to retain learned aversions compared with birds [20], and mantids will readily feed on aposematically colored harlequin bugs that are noxious to birds [18]. Collectively, these results highlight the novel and unexpected insights that can be gained from examining diverse predators.…”

“…Recent studies have emphasized the importance of considering a more diverse set of predators in this work [16,17], with a particular emphasis on considering terrestrial invertebrate predators [18][19][20][21][22][23][24], and such studies are revealing surprising insights. In some cases, there are remarkable similarities between arthropod predators and birds; for example, similar (but not identical) patterns of color aversion, learning, and generalization have been shown in jumping spiders [19][20][21]24], mantids [25], and predatory wasps [26,27].…”

Response of adult dragonflies to prey of different size and colour in the context of anti-predator defences

“…Harlequin bugs (Tectocoris diophthalmus) painted bright orange, placed on a leaf, were cryptic to mantids from afar but could induce avoidance learning in birds. In the same system, Fabricant and Smith (2014) found that the same bugs (naturally colourful and iridescent) were conspicuous (hence aposematic) to domestic chicks but not mantids, which emphasizes the importance of testing multiple, ecologically relevant predators.…”

“…The practice of considering more than one predator type (and its' subsequent behaviour) has been less prevalent in the study of animal coloration and aposematism as literature has continually focused on behaviour and cognition from a single perspective and far fewer studies have investigated other prey taxa. Fabricant and Smith (2014) discovered that aposematic Harlequin bugs were aposematic to domestic chicks but not to praying mantids (they also observed assassin bugs, lynx spiders, and orb-web spiders feeding freely on these bugs). Further, Pearson (1985) offered tiger beetles (Cicindela spp.)…”