They’re the insect version of a handgun, known for the world’s most painful sting. These bullet ants (Paraponera clavata) hold a venom that can leave victims in agony for weeks.
Entomologist Justin O. Schmidt, creator of the Schmidt Sting Pain Index, rated a bullet ant’s sting as the absolute worst, describing it as “pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a three-inch rusty nail in your heel.”
The ants, which can grow to be more than an inch long, nestle at the base of trees in La Selva Biological Reserve of Sarapiquí, Costa Rica, and come out to forage during the day. The female workers seek food, and are usually infertile. The males and others inside the nest are in charge of cleaning, tending the larvae and taking care of the queen.
University of Arizona entomologist Jennifer Jandt, Ph.D., is studying the social behavior of bullet ants when it comes to eating behaviors.
Jandt’s work is part of a research program run by Terry McGlynn, associate professor of biology at California State University, Dominguez Hills.
In the early morning of July 23, Jandt tightened the laces on her rain boots, grabbed a hat to cover her long brown french braid, and embarked on a trail leading deep into the La Selva rain forest. She paused to carefully examine each tree that had previously been marked with an orange flag – an indicator of bullet ants’ location. With no ants in sight, she turned and said, “Well, this is why I didn’t want to come out when it was raining.”
Jandt is followed by her assistant, Peter Tellez, a graduate student at California State University, Dominguez Hills.
A gang of howler monkeys loom in the distance – their deep grunts sounding like they belong to a tremendous gorilla, rather than the small creatures that they are. A nearby tree branch falls a couple of feet ahead on the trail, rustling leaves all the way to its final “thump!” as it hits the ground, causing us all to jump. It feels like a scene from “Jurassic Park.”
At noon, when the rainfall ceases, we continue our search for bullet ants. The air thickens with humidity and mosquitoes, wasps, dragonflies and multitudes of insects. Swatting away, Jandt proceeds in her boots, jeans and T-shirt, carrying a plastic container full of 15 droppers and glass bottles of her solutions she will test on bullet ants living at the base of the trees. The second time around, she was not let down. The bullet ants were out, foraging in trees by the dozen.
“You can’t just study within a colony,” Jandt said. “I’m trying to conduct a study of the many individuals within a colony, but also get a range of many colonies so I have a really good picture of this general behavior.”
When bullet ants spot a fruit nectar it is common for them to lap the sugar juices from it, sipping and transporting it back to their nest in their mouths. They exhibit the same behavior for most liquids.
Hannah Larson, another insect researcher working with Jandt at La Selva, had noticed that when bullet ants approached a water solution with protein, they used their mandibles to pull and chomp at the protein water solution, much like they would do with the flesh of prey before ingestion. Though she was conducting a different study on bullet ants, she mentioned this behavior to her mentor, Terry McGlynn. McGlynn met with Jandt at a conference, and offered her the chance to probe further into Larson’s observations.
Jandt decided to also see why the ants didn’t lap up samples of a protein liquid, which looked identical to sugar water, in their mouths. Jandt traveled to Costa Rica from Tucson, Arizona, to begin her study. Her field work included distributing samples of her lab-made combinations of sugar water and protein water, on several different bullet ant nests.
She has made note of a variety of odd approaches the bullet ants have to the water with different concentrations of sugar (sucrose) and protein (casein): some pick at it, or probe it with their antennae, some bite or snap at it, and some even playfully lick it.
Jandt’s intention was to collect 750 data points from 15 different nests in the rainforest of the La Selva Biological Research Institute to observe how the bullet ants reacted case-by-case with each different solution. Her goal is to answer one question: At what point do the bullet ants differentiate between protein water and sugar water? Some of the 15 samples are a mixture of both, with higher percentages of either protein or water.
Before collecting her first data sample on this hot July day, Jandt pins a dropper containing a high-sugar solution to draw ants to forage up the tree for a refreshing drink. As soon as a group gathers around the dropper, she switches it out for another identical one.
“They’re not going to like that,” she said.
This first dropper, numbered “4,” contained a mixture with more protein than water. Tellez covered the number while handing the new dropper to Jandt, so she would be blind to the experimental sample. She simply observed the behavior, shouting out her notes as Tellez wrote them down in a notebook.
The 15 droppers she interchanged contained a ratio of protein to sugar water solution that ranged from high-sugar/low-protein water solution to high-protein/low-sugar water solution, and everything in between.
After her return to Tucson Aug. 3, Jandt plans to share the results of her research with other scientists.
“Sometimes, discovering patterns that ideally work within an insect’s social group, can also be used to apply to human systems,” she said. “The way animals interact can teach us many things, like how we, for example, use division of labor.”