Biology Research: The curious case of the ant-mimicking spider
Nandita Jayaraj explores how one crafty arachnid and two inquisitive ecologists, Divya Uma and Krishnapriya Tamma, inspired Nimish Anil, an undergraduate student of biology, to pursue a life in research.
As Nimish Anil watched the weaver ants they had collected scurry around inside a petridish, they noticed something strange. Many of the ants had gotten themselves stuck… within a silky material that wasn’t there before. It seemed that one of the ants was producing the silk. This is something different, Nimish thought. Ants can’t spin silk, can they?
Though just out of school, Nimish was no stranger to the quirks of nature. They had been an avid birdwatcher since their early teens, and having lived for a while close to a tiger reserve, long walks in the wilderness were a routine affair. “Birds aren’t always there, so instead we would observe flowers, insects and spiders.”
Yet, Nimish had never encountered a silk-spinning ant before. They turned to their professor at Azim Premji University, Divya Uma, for some answers. Divya, a seasoned biologist, informed Nimish that the rogue “ant” in their petridish wasn’t an ant at all, but a spider!
Specifically, it was a species of jumping spider that has evolved to resemble an ant, as a protective tactic. By pretending to be a weaver ant, this spider was warding off hungry predators which are wary of the ant’s notoriously vicious bite and off-putting taste.
“I was mindblown. This was nature being completely crazy,” said Nimish, whose tryst with these creatures was only beginning.
Several conversations, observations and literature reviews later, Nimish decided to study the behaviour of these spiders more closely.
How did the ant-mimicking spiders behave in the presence of ants, and was this different from how they acted in front of their non-mimicking jumping spider cousins? How exactly were eight-legged arachnids managing to look so much like six-legged insects? Was it by mimicking their walk? Could scientific tools be used to determine how similar the two species actually were?
Nimish’s honours thesis was the perfect opportunity to pursue this curiosity, and lucky for them, a much more experienced Divya was ready to guide them through their first formal research experience.
Things got even more interesting for Nimish when another faculty member, Krishnapriya Tamma, offered to help them add a dimension to their study with her expertise in a field called morphometrics.
Comparing the body shapes and behaviour of organisms through Morphometrics
In biology, morphometrics deals with the quantitative analysis of the morphology, or form, of living organisms. With Krishnapriya on board, Nimish would be equipped to not just compare the behaviour of these spiders and ants, but also their body shape. To the naked eye, the two looked similar enough but only numbers and analyses could confirm how strong their similarity in form actually is.
As much as Nimish valued Krishnapriya and Divya’s expertise, they found that it was just as inspiring to watch the two biologists in their element. “I really liked hearing the excitement in their voices, the give and take between them. If I get to just 5% of their level — where I can think and do stuff, connect the dots and understand the workings of nature, like they do — that would be awesome!” said Nimish.
The hunt for samples
To kick off their study, Nimish first needed to secure samples. Observations require live models, so Nimish spent many days peering under leaves and squinting at crevices on walls to spot the tell-tale hammocks that these ant-mimicking spiders rest inside.
They looked for specimens around the Sompura area (where the Azim Premji University, Bengaluru campus, is located), as well as in and around the large Indian Institute of Science (IISc) campus in Bengaluru city. In comparison, weaver ants and regular jumping spiders were easier to find.
For the measurement part of their study, live models were no good. Nimish used frozen samples that had been earlier preserved in the lab. These preserved samples were tricky to work with because they were prone to breaking.
However, this helped Nimish minimise the number of ant and spider sacrifices they would have to make. “The measurements could get gory. We needed to measure each part of their legs, so we would cut the leg from the body, put each individual leg under the microscope, take pictures and then use the image analysis software. In all, we took about 1,500 measurements,” they said.
Naturally, the COVID-19 lockdown declared in 2020 threw a spanner in the works. Nimish and Divya were looking to expand their sample size, so the show had to somehow go on. This is where things got really interesting.
“I had to leave the University, so I didn’t have access to labs. Divya would mail me the specimens. I made a makeshift imaging set-up with my mobile phone, a magnifying glass and a surgical blade. Luckily, I managed to get good images and I could continue my work. It was chaotic, but it gave me something to do during the lockdown!” reminisced Nimish.
Has the spider perfected the art of mimicry?
Nimish, Divya and Krishnapriya’s efforts paid off. Their analyses threw up several eye-opening results, but most illuminating for Nimish was the revelation that despite how alike the mimic spider and ant may seem, in reality, it was only an intermediate degree of similarity.
“In terms of movement, the spiders were more accurate mimics of the ants. But in terms of body shape, there were discrepancies. They looked just alike enough to fool their predators. That’s enough for their mimicry to work,” summed up Nimish. The paper the team wrote is now under review. As one of the few quantitative studies that have been done on ant-mimicking spiders, Nimish is optimistic that their study will get published in a journal.
Nearly five years after that first encounter with these crafty arachnids, Nimish is now busy wrapping up their Master’s degree at a college in Pune. Research is something that they plan to continue with.
“I was mindblown by the lives of these mimics and the kind of adaptations they have evolved just to escape predators. But more enriching for me was the experience of working with Divya and Krishnapriya,” they said.
“They are both exceptionally brilliant minds, but also very kind human beings. They valued my opinions, trusted me to explore and be independent. That environment helped me believe in myself. With their support, this became a beautiful experience.”
Watch Divya Uma and Krishnapriya Tamma in conversation about Nimish’s project here:
Learn more about Azim Premji University’s Biology programme here:
Read more about ant-mimicking spiders: https://roundglasssustain.com/species/when-spiders-mimic-weaver-ants
Read Nimish, Krishnapriya, and Divya’s journal article: https://doi.org/10.1093/beheco/arac104
Know more about Divya Uma and Krishnapriya Tamma, Biology faculty members at Azim Premji University.
Note: Nimish Anil’s preferred pronouns are they/theirs/them.
About the Author
Nandita Jayaraj is a Science writer and Communications Consultant at Azim Premji University.