Hunted Becomes Hunter as Moths Mimic Spiders

The jumping spider, Phiale formosa. It is mimicked by the metalmark moth, Brenthia hexaselena. Credit: Jadranka Rota

The metalmark moth, Brenthia hexaselena (top and bottom). It mimics the jumping spider, Phiale formosa. Credit: Jadranka Rota

In the animal world, some species often mimic the appearance of other species for protection against predators. For instance, many butterflies mimic the monarch butterfly, which taste awful and thus avoid being consumed by predators.

Scientists have now discovered that metalmark moths in Costa Rica use mimicry to escape hunters as well, by mimicking the very predators that might normally eat them.

Intriguingly, the predators in question--so-called jumping spiders--may also get mimicked by a variety of flies and butterflies. Ironically, some jumping spiders mimic ants to avoid getting devoured by them.

"Crazy things happen with mimicry and this is another such example," said researcher Jadranka Rota, a lepidopterist at the University of Connecticut in Storrs.

Rota was exploring the forests of Costa Rica when metalhawk moths perching on leaves near her suddenly flared their wings "in a really strange way, and then they jumped around," she told LiveScience.

Jumping spiders are common predators in these habitats. These territorial hunters track prey with their eyes, and their vision is sharp, capable of making out details 40 body lengths away. The spiders often move in short, rapid, jerky motions.

In experiments, when metalhawk moths were cooped up with jumping spiders, Rota and her advisor David Wagner found the spiders only caught the moths only about six percent of the time. On the other hand, when normal moths and jumping spiders were caged together, the spiders caught the moths roughly 60 percent of the time.

Predator mimicry appears exceptionally rare in nature. "We don't know enough about the mechanisms that are driving these systems, and that is something that would be interesting to explore," Rota said.

Still, a number of species unrelated to metalhawk moths may also mimic these spiders. For instance, tephritid flies are known jumping spider impersonators, while a variety of moths and other insects have similar coloration and perching patterns. Such mimicry means "you'll survive frequent encounters with these spiders, and that seems like a great advantage," Rota said. "

Rota and Wagner reported their findings December 20 in the inaugural issue of the journal PLoS ONE.

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