Spider mimics

by MARGARET COULOMBE

photos courtesy Lisa Taylor

A female Phiale formosa seen in the rainforest of Costa Rica. While the female spider apparently mimics a wasp, the male of this species is colored black and white to mimic a completely different species of velvet ant.A female Phiale formosa seen in the rainforest of Costa Rica. While the female spider apparently mimics a wasp, the male of this species is colored black and white to mimic a completely different species of velvet ant.

You are an ant in the wilds of the Costa Rican jungle. Most likely, you are surrounded by thousands of your best friends. Actually, to be totally accurate, they are your sisters. As a result, the most likely creature you'll see is a near perfect copy of yourself. That creature is sleek. It has three body segments—head, thorax and narrow abdomen. It has long, waving antennae. Correct?

Not necessarily.

Ants have notoriously bad eyesight. A closer look at the neighbor could reveal a row of eyes, rather than just two. And what's waving in the air like a sister's antennae might actually be a pair of legs.

What ant is this? Sorry. It's not an ant at all. The familiar-looking creature is a spider in ant's clothing, an ant mimic.

Myrmecomorphy is the technical term for the mimicry of ants. Such mimicry is widespread in spiders. It is most common in Salticidae, a family of jumping spiders.

Lisa Taylor studies these mimics. She is a doctoral student in the School of Life Sciences at Arizona State University. With a fellowship to attend a field course with the Organization for Tropical Studies in Costa Rica and digital camera in hand, Taylor dogged the steps of jumping spiders in the tropical jungles of La Selva. She also tracked them through the halls of the Smithsonian Museum in Washington, D.C.

Taylor discovered that while some jumping spiders blend in with vegetation or groundcover, such as bark and sand, others mimic ants and wasps to escape predation.

Why look like an ant? In the tropics, the prevalence of ants, particularly ants with a nasty stings or bites, gives spiders some protection from predators. Birds, wasps, and lizards enjoy a spider meal. Ant parody also gives spiders access to areas typically off-limits to hunt and hide.

Looking like an ant can lead to an easy meal. Some of the myrmecomorphic spider species take their look-alike mimicry one step further. Not only do they appear to be ants, they smell like them as well.

Makes sense. Ants communicate by chemical signals. Some jumping spiders have come to exude chemicals that say "ant" to potential ant colony defenders. These chemicals make it possible for the jumping spiders to come and go unmolested in an ant nest. The faux scent provides protection from larger predators and unlimited access to ant larvae on which to dine.

Other myrmecomorphic jumping spiders take another tack. They mimic uncommon, but noxious insect species, rather than abundant ones.

For example, velvet ants are wingless wasps that resemble large fuzzy ants. They are rare, but brightly colored. Their color gives notice to potential predators that they have a painful sting. Looking nasty in this case seemingly gives a survival advantage to the velvet ant spider mimic, in addition to the velvet ant they're modeled after.

The black and orange spider Phiale mimica (right) is found in the same Costa Rican habitat as the velvet ant Dasymutilla cressonii (left).The black and orange spider Phiale mimica (right) is found in the same Costa Rican habitat as the velvet ant Dasymutilla cressonii (left).

Taylor explains that there are four types of mimicry: Wasmannian, Mullerian, Peckhammian, and Batesian. There are more than 19 species of ant mimics from 10 genera of jumping spiders in La Selva alone.

Why so many mimics? Survival is the simple answer.

In the tropics, predators are surrounded by many dangerous potential prey items. A mistake can be costly, Taylor says. So looking like something irksome adds up to evolutionary advantage, particularly for myrmecomorphic jumping spiders in areas that abound in ants.

Listen to an "Ask a Biologist" podcast with Lisa Taylor  speaker.jpg


The research is supported by the National Science Foundation's Graduate Research Fellowship and small grants from Sigma Xi, The Animal Behavior Society, Graduate and Professional Student Association, and the Organization for Tropical Studies. For more information, contact Lisa Taylor, School of Life Sciences, College of Liberal Arts and Sciences, 480.620.6053. Send email to Lisa.A.Taylor@asu.edu