Mindanao Mimics
There’s a species of jewel weevil called Pachyrhynchus reicherti. Its black and spotted body has a unique pattern. Its elytra are fused together. It cannot fly. Most predators know to stay away. It’s too tough to bite through. Its strong colors and markings indicate that it would be a waste of a hungry predator’s time.
When Cabras first spotted Metapocyrtus willietorresi—a new species—she mistook it for Pachyrhynchus recherti. It has similar colors and markings. It has tough, fused elytra. Neither beetle would make a good meal. So, why was one “copying”
the other?
It’s all about educating the predators, she says. Warning colors work because predators learn that they represent foul-tasting, dangerous, or even poisonous outcomes. Over many generations, predators learn to stop eating anything that looks a certain way.
In science, this phenomenon is called Müllerian mimicry. That’s when two equally harmful things have evolved to resemble each other. By having similar colors and patterns, they both stay safe from predators.
It doesn’t end there. There’s a third beetle to this story: Doliops daugavpilsi. This beetle looks a lot like the other two. Except this beetle is not a jewel weevil. It’s a longhorn beetle. And though it may look tough like the other two weevils, it isn’t. It has a soft shell—one that predators could easily bite through.
Pachyrhynchus reicherti
Metapocyrtus willietorresi
By having colors and patterns similar to the weevils, the longhorn stays safe. This is called Batesian mimicry. In this form of mimicry, an edible insect with few defenses looks like a dangerous one, so predators stay away.
During her field work, Cabras started finding a lot of beetles that looked similar to each other. “I got fooled many times,” says Cabras.
Here are a few examples of the beetles Cabras found during her fieldwork on Mindanao. The mimics strongly resemble their models.
MODEL
Model: Metapocyrtus kitangladensis
MIMIC
Mimic: Coptorhynchus sp.
MODEL
Model: Pachyrhynchus tikoi
MIMIC
Mimic: Metapocyrtus sp.
To test a hypothesis, Cabras used fake beetles made of modeling clay, like the one shown here, to see if predators would react to the beetle’s warning colors.
Testing a Theory
Cabras began to wonder if she was the only one being fooled. She wanted to try an experiment. She and her team made fake beetles out of modeling clay. The fake beetles looked like Pachyrhynchus recherti. She set them out in places where these beetles were common. She also set them out in places where they were not. Then she set up cameras to see what would happen.
Where the beetles were common, predators avoided the clay beetles. They had learned what those colors and patterns mean. In the places where the beetles were less common, more predators attempted attacks. These predators had not yet learned to stay away.
Cabras still has many questions she wants answers to, and there could be many more new species waiting to be discovered. While her work must be careful and meticulous, Cabras says a lot of land on Mindanao is being cleared away for farming and houses.
a camera trap
In Mindanao, there could be many new species to discover.
“It’s really scary for me. As a taxonomist and conservationist, I really do hope to see these beetles in their natural habitats. But in five to 10 years, I’m not really sure if I go back to that area, if I can still find those species. The small area where the four new beetles were found? It is slated to be cleared soon for farmland.”
With a sense of urgency, Cabras is doing her best to discover, observe, and document the biodiversity that she sees in Mindanao. She thinks “every taxonomist has a special eye.” And for now, Cabras’ eyes are trained on weevils.