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The dangerous game of the 'highwayman' beetle

This beetle is good at getting ants to feed it — but it better not get caught.
August 18, 2017

ASU researchers detail the perilous impersonation nitidulid beetles do in order to trick ants into giving them food

We all know the type. The project co-worker who doesn’t really work on the project, but shows up for the group photo. The dinner companion who develops alligator arms when the check appears. Shirkers. Goldbrickers. Idlers. Malingerers.

Imagine outing them, then ripping off their ears, arms and legs.

This is the dangerous game played by the nitidulid beetle. It disguises itself as an ant, lurks along their foraging trails and tricks them into giving it food. The beetle is so good at deception that it gets more food from ants than ants get from their fellows.

But if the ants find out, reprisal can be brutal.

A paper published by a pair of Arizona State University scientists this month detailed this practice. It’s a glimpse into a world inside ant colonies resembling a cross between a World War II spy thriller and “Invasion of the Body Snatchers.” In that world there is deception, drama, subterfuge and ruse de guerre. Insects disguise themselves as ants or mimic ant behavior to successfully live hidden in plain sight amongst ants.

“The insect superorganism is ... full of such commensals (parasitic organisms that don’t harm their hosts),” said co-author Bert Holldobler, a sociobiologist and an evolutionary biologist in the School of Life Sciences at ASU who studies the evolution of social organization in insects. “Many of them have evolved different degrees of adaptations to the social habits of their ant hosts.”

Ants feeding nitidulid beetles. Video courtesy of Bert Holldobler

Creatures that live with ants are called myrmecophiles. Christina Kwapich, a postdoctoral researcher who co-authored the paper with Holldobler, studies them. She explained how nitidulid beetles buffalo the ants.

“We refer to them as highwaymen beetles, because they’re robbing the traffic lines of the ants,” Kwapich said.

Ants go out on massive foraging trails to collect honeydew from little insects like aphids. They fill a social stomach, which is an enlargement of their esophagus, with their crop. In that crop they have this sugary liquid that they can share with their own nestmates through mouth-to-mouth regurgitation (a process called trophallaxis).

“It’s that behavior that this parasitic beetle has sort of capitalized on,” Kwapich said. “It’s broken the code of communication between the ants in order to steal that sugary liquid that’s meant for other nestmates. What the beetle does, what Bert discovered, is it sits along the sides of these foraging trails and populates the nest entrance area and waits for returning foragers with their crops laden with sugary liquid.”

The beetle is able to steal quite a bit of liquid. They actually get more of the food than the other ants do: 1.8 times as much food. They’re true parasites.

“We like to think of what the sensory world of the ant is, and it’s mostly tactile and chemical,” Kwapich said. “It’s those features that the beetle has used to break the code of feeding.”

The food transfer is a one-way street. The ants are feeding the beetles, but the beetles are not giving it back.

ASU postdoctoral researcher  examines insects through a microscope

Christina Kwapich

“Also, the beetles aren’t giving it to each other,” she added.

All the beetle had to do to evolve is to break a simple communication code the ants use to solicit food from nestmates, Holldobler said.

“Employing radioactively labeled honey water, we were able to measure how successful the beetle is soliciting food from the ants,” he said. “It turned out that his food-begging behavior is good enough to receive food from workers that carry honeydew in a full ‘social crop,’ but not good enough to receive food from workers inside the nest.”

The beetles also have a kind of Mata Hari seduction trick scientists have observed but not yet cracked. They have glands in their head and around their mouths which secrete some sort of appeasement compound.

“At the beginning of the interaction, where the food stealing is happening, the ant is transfixed by the secretion the beetle makes,” Kwapich said. “We don’t know what that substance is.”

The beetles aren’t always successful, but, if discovered, they have some adaptations they can deploy to save themselves. The ants will try to flip the beetle over. If they can accomplish this, they will tear off the beetle’s antennae and legs.

“They don’t always work, but what they do have is legs covered in brushy hairs that allow them to grip the ground,” Kwapich said. “They have a shell with these little wings on it that flatten. When an ant perhaps notices the beetle isn’t an ant, the beetle can really suction itself to the ground. It makes a perfect little cup on the ground that’s difficult to pry up. Occasionally the ants can pry the beetle up and kill it. It is a dangerous game for the beetles to be playing, but they’re pretty good at it.”

Holldobler considers highly evolved social insect colonies, such as most ant societies, as superorganisms.

“All organisms, including our own, provide ecological niches for all sorts of other organisms,” he said. “Some are beneficial symbionts, others make their living as benign parasites, and again others are deadly pests. This is also the case with superorganisms of social insect societies.”

In the 16th and 17th centuries, Navajo raiders struck Spanish settlements along the Rio Grande every year, but they always left enough turkeys and sheep so that there would be more next year. They stole a little, not a lot. The beetles do the same thing. (Some ants do it as well when raiding rival colonies, according to Kwapich.)

“It’s not occurring at high enough numbers to affect the success of the colony,” she said. “The colony still survived for many years and they were still able to reproduce. The beetles are occurring at a low enough abundance that the colony still survives to be parasitized.”

Ant crickets in an ant colony

The ant cricket — Myrmecophilus manni — steals food from ants by rubbing against the ants to acquire their odor, allowing it to blend in with the tiny insects. Some are pictured here in the Insect Rearing and Behavior Lab on ASU's Tempe campus on Aug. 16. Photo by Charlie Leight/ASU Now

Most myrmecophiles mimic the smell of the nest they live in. Ants are covered in a waxy hydrocarbon substance, which is how they identify each other and their nest. Crickets and other myrmecophiles don’t have this substance. They will comb ants with special tools like brushy mouth parts or leg bristles and anoint themselves with it. Crickets will walk under ants, rise up and rub themselves against the ants.

“This is all to maintain the chemical mimicry that’s allowing the ants to be blind to them in the nest,” Kwapich said.

Myrmecophile spiders can live undetected amongst the ants they prey on.

“If you switch them to another nest they will actually molt their cuticle,” she said. “They’ll get rid of that old smell as rapidly as possible.”

Other beetles live inside ant nests. They have adoption glands that encourage ants to pick them up and bring them inside.

“Again, they’re using the chemical communication signals of the ants and they’re using a glandular secretion to inspire the ants to bring them in,” Kwapich said. “They also have appeasement glands which secrete a substance the ants find attractive, and they have defensive glands for when things get ugly. They have cracked the chemical code of the ant language.”

Even some vertebrates are myrmecophiles, like snakes, lizards, frogs and birds.

“Most of what we work on in this lab are other invertebrates,” she said. “Here in the lab we have one of my favorite myrmecophiles, Myrmecophilus manni. It is one of the tiniest crickets in the world. ...

“The interesting them about them is they are generalists; they don’t live with one specific kind of ant host. They live with many different ants. Depending on the ant they live with, they reach a different body size. You can get really big ant crickets if they live with a big ant host. That’s one of the mysteries we’re trying to solve in our lab right now.”

Top photo: ASU postdoctoral researcher Christina Kwapich looks at a sample collection of ants with an ant cricket in the Insect Rearing and Behavior Lab in Tempe. Photo by Charlie Leight/ASU Now

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ASU student passionate about advancing gender equality in the business world

New student Priyanka Mathur is ready to tackle gender inequality in business.
August 18, 2017

Drawing inspiration from her mother, Priyanka Mathur sees women as having no limitations

Editor's note: This is part of a series of profiles of fall 2017 incoming ASU students.

Priyanka Mathur has already accomplished a lot, working as a high-level marketing professional at a major corporation and winning a spot in a highly competitive MBA program at Arizona State University, yet one of her biggest inspirations remains her mother.

“I was working with Siemens, responsible for all India marketing and strategy for industry services and I was really fortunate to find this great responsibility at a very young stage in my career,” said Mathur, who is in the full-time Forward Focus MBA program in the W. P. Carey School of Business at ASU.

She appreciates the school’s attention to increasing the number of women in business — a trend she’s passionate about.

“My earliest source of inspiration was my mother. She was the first woman police officer in Rajasthan,” the largest state in India.

“India is a very conservative country and Rajasthan is one of the most conservative states, so back in the 1970s it was really difficult for women to find challenging careers and to challenge the system. And my mom was one of them,” she said.

“So I feel there are no limitations to women’s capabilities and they’re equally strong as men.”

Although women are graduating from college in numbers equal to men, Mathur notes that women are drastically underrepresented among CEOs at the largest companies.

“As of 2017, there are 32 female CEOs on the list of Fortune 500, meaning that only 6.4 percent of the U.S.'s biggest companies are run by women and this is the highest proportion of female CEOs in the 63-year history of the Fortune 500,” she said.

“Post MBA, I want to be a successful business leader and a trusted adviser to aspiring women. Gender equality is the vision of my generation and I want to be at the epicenter of the movement.”

Meet Priyanka Mathur:

Question: Why did you want to pursue a Forward Focus MBA at ASU?

Answer: I am keen on exploring and harnessing the potential of data analytics in marketing and operations. W. P. Carey’s highly ranked Forward Focus MBA Program will not only provide me deeper insights on expanding my knowledge base on data analytics to solve complex business problems, but also help me hone my leadership skills to effectively collaborate and lead across various cross functions at a global level.

Q: What are you most excited to experience your first semester?

A: The firsthand experience of interacting with people coming from 24 nations and understanding different cultural nuances that come to play both in business and in real life.

Q: What do you like to brag about to friends about ASU?

A: We have all the numbers to brag about. We are U.S. No. 1 school in innovation, No. 3 in supply chain, No. 25 in global MBA program; the list goes on. But what I would like to brag about is the feel of being a part of this small close-knit community where everybody wants to help each other. This makes ASU an ideal environment conducive towards learning for growth and development.

Q: What talents and skills are you bringing to the ASU community?

A: My professional network finds me as a creative problem solver and an articulate communicator. My solid background in marketing and project management will enable me to contribute in various team-based projects, case-studies and classroom discussions, especially in courses such as service innovation and business-to-business marketing.

Q: What’s your favorite TV show right now?

A: “Game of Thrones.”

Q: What do you hope to accomplish during your MBA study?

A: I seek to understand business from a global perspective, gain cross-cultural experience and acquire a growth mind-set to advance my career towards being a global business professional in my niche.

Q: What’s one interesting fact about yourself that only your friends know?

A: I’ve been writing in my daily diary since I was 15.

Q: If someone gave you $40 million to solve one problem in our world, what would you choose?

A: Back in the 1970s, a woman police officer was unheard of across the country. Ms. Pramila Mathur rose up to the challenge and fought her way through the system to make it happen. I have been fortunate to watch this amazing woman every day of my life because I am her daughter. Since childhood, I have firmly believed that gender is no ceiling to capabilities and aspirations.

Currently, the representation of women in business is far from ideal. MBA is one of the primary pipelines for supply of future leaders. And clearly there is a dearth of women leaders in the business world. I believe a financial stimulus could accelerate things. Taking inspiration from ASU’s Forward Focus program, I will like to start a fund. Potential women candidates who have the ability but lack means need to be identified across the world and must be trained extensively to become our future business leaders. With $40 million, I can make a start toward bringing a shift in the current scheme of things.

Top photo: Priyanka Mathur is in the Forward Focus MBA program in the W. P. Carey School of Business. Photo by Charlie Leight/ASU Now

Mary Beth Faller

Reporter , ASU News