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. It’s too tough to bite through. And its strong colors and markings tell predators to stay away.
When Cabras first spotted a new species, Metapocyrtus willietorresi, she mistook it for Pachyrhynchus reicherti. 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?
The phenomenon is called Müllerian mimicry. That’s when two equally harmful things have evolved to resemble each other. When beetles have similar colors and patterns, predators learn that they represent dangerous, foul-tasting, or even poisonous beetles. And predators stay away.
It doesn’t end there. A third beetle, Doliops daugavpilsi, looks a lot like the other two. It’s a longhorn beetle. It has a soft shell—one that predators could easily bite through.
By having colors and patterns similar to the weevils, the longhorn stays safe. This is Batesian mimicry. An edible insect with few defenses keeps predators away by looking dangerous.
Here are a few examples of the beetles Cabras saw during her fieldwork on Mindanao. The mimics strongly resemble their models.
To test a hypothesis, Cabras used fake beetles made of modeling clay, like the one shown here. She wanted to see if predators would react to the beetle’s warning colors.
Testing a Theory
Cabras wondered if she was the only one being fooled by these look-alikes. She tried an experiment. She and her team made fake beetles from modeling clay. They looked like Pachyrhynchus reicherti. She set them out in places where these beetles were common and 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 tried to attack. They had not yet learned to stay away.
In Mindanao, there could be many new species to discover.
Cabras still has many questions she wants answers to. But a lot of land on Mindanao is being cleared away for farming and houses. In five to 10 years, she might not be able to find these beetles in their natural habitat.
With the clock ticking, Cabras is doing her best to discover, observe, and record the biodiversity that she sees in Mindanao. For now, her eyes are trained on weevils.