One uncommon form of mimicry in the animal world is predator mimicry- when prey mimic their predator to avoid being eaten. This is the case with the jumping spider and certain species of moth. However, this is not simply mimicry in appearance—these moths are able to mimic their predators movements as well. In particular, the jumping spider often jumps or displays a leg lifting behavior in territorial or mating displays.
a) ‘Peacock-like’ display of B. coronigera; b) C. hyligenes; c) Leg raising as courtship in jumping spider Menemerus fulvus
Previous studies have indicated that moths that are able to mimic this behavior as well as the appearance of the jumping spider are more likely to evade capture. One study by Mu-Yun Wang and authors delves further into this question. They studied two species of mimicking moth, Brenthia coronigera and Choreutis hyligenes. Both show jumping behavior while on vegetation, while only the former shows an additional peacock-like display showing eyespots and stripes that look quite like spider legs. These two species were contrasted with a non-mimicking moth, Corcyra cephalonica as a control species. These moths were tested against four different species of jumping spider. The researchers hypothesis was firstly that the moths with more components in the signal (B. coronigera) would deter predators more than the moths with a slightly simpler signal. In addition, they hypothesized that each separate component of the signal would contribute significantly to the mimicking effect.
B. coroniga (Wiki Commons)
To test these hypotheses, the researchers first tested each moth species separately with jumping spiders and recorded the time to the first attack, time to the moth’s death, and duration of the leg raising behavior. The leg raising behavior is a particularly essential component, because it is only used during territorial and mating signaling. For a spider to use it in communication with a moth indicates that the spider has been fooled by the moth’s mimicry. The same process was then repeated with the moths frozen in different signaling positions to separate the signal components. Additionally, eyespots were painted over on some moths to assess the significance of that part of the signal.
The authors found that only B. coronigera was truly able to mimic the jumping spiders, proving the first hypothesis. The survival of that species was significantly higher than that of C. hyligenes, while the survival of C. hyligenes was not significantly higher than that of the control. The species of the jumping spider had no effect on the survival of the moth. Across the board, significantly more spiders performed leg raising behavior when presented with B. coronigera. Additionally, they found that all signal components contributed to the mimicking effect, proving the second hypothesis.
Survival curves for all three moth species. Different letters indicate significant difference.
This led the authors to draw the conclusion that the B. coronigera moths are able to survive by tricking the spiders into thinking that they are also spiders. Since the loss of any single component reduced (but did not negate) the success of the mimicry, it is clear that the presence of eyespots–which only B. coronigera possessed–is crucial. Additionally, it is clear that with the high diversity of jumping spiders, it is more beneficial to have a generalizable display that can affect a wider variety of potential predators.
While this study answers many questions in the field, it has yet to address the possibility that some of these displays may not be targeted at spider predators at all. This is one question that further work may be able to eludicidate.
Sources:
Wang, M-Y., Vasas, V., Chittka L., and Yen S-H (2017). Sheep in wolf’s clothing: multicomponent traits enhance the success of mimicry in spider-mimicking moths. Animal. Behavior. 127, 219–224.
