How the mini spider Siler collingwoodi irritates its predators
Beijing. With a double trick, a small spider tries to protect its life. The jumping spider does not hop like related species, but imitates feelers with its front legs and walks like an ant with the other six legs, Chinese researchers report in the journal “iScience”. In addition, it is exceptionally colourful. This unusual mix of mimicry and camouflage works well in many cases, but praying mantises remain a threat.
Spider mimics different species of ants
Ants are often very defensive with their jaws, and some also use chemical repellents. Several species of spiders mimic the six-legged creatures to deter potential predators. However, they are usually as dark in color as ants and not as brightly colored as the tiny jumping spider Siler collingwoodi, the scientists explain.
The team collected spiders of the species in Hainan province and tested under laboratory conditions whether they were less likely to be spared predators than other jumping spider species. “From a human perspective, it seems to blend in well with the plants around it, but we wanted to test whether its body color really serves as camouflage to protect against predators,” said Hua Zeng of Peking University, first author of the study.
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The researchers characterized and compared the movements of the spiders with those of different ant species – in terms of the use of the individual limbs, the speed and the chosen trajectory (straight or coiled). According to this, the running style most closely resembled that of small ant species. “Siler collingwoodi is not necessarily a perfect mimic of any particular species, its gait and trajectory closely resembled several species of ants,” Zeng explained. “General mimicry, rather than perfect imitation of just one species, can be an advantage for the spiders when colonizing different habitats.”
How predators react to the spider
The team also tested the response of two potential predators to the colorful jumping spider: a similarly sized color-sighted jumping spider (Portia labiata), which specializes in hunting other spiders, and a monochromatic-sighted praying mantis (Gonypeta brunneri). Either red-flowering West Indian jasmine (Ixora chinensis) or fukien tea (Carmona microphylla) was used as a background. Spiders also occur naturally on both plants.
According to the tests, the colorful spiders on the red jasmine flowers were less likely to be prey to the predatory spiders or praying mantis than on the green tea leaves. In further experiments, the two predators were given the choice between Siler collingwoodi and another jumping spider that did not imitate ants. The predatory spiders chose the more harmless-looking relatives far more frequently – the praying mantis, however, attacked both types of prey with equal readiness.
The much larger praying mantises are less at risk of being seriously injured by defensive ants and therefore do not avoid them, the researchers suspect. All in all, the following applies: Siler collingwoodi, with its camouflage coloring, is more likely to be spared attacks, especially in front of a suitable colorful background – its imitation tactics, on the other hand, only work with predators who keep a respectful distance from ants.
RND/dpa
