Welsh-born Seirian Sumner has seen many a wasp-nest soap opera unfold in the steamy jungles of Asia and Central America. But what she witnessed during a 2005 field season in Panama led her to some groundbreaking revelations about the evolution of insect social behavior.
As with most social insects, Panamanian paper wasp workers forsake their rights to reproduce for lives spent tending to the queen’s brood. Because nestmates are all genetically related, wasps preserve their own genetic legacy by seeing to the survival of the whole nest. That’s why Sumner was intrigued when she’d spot the occasional worker flitting about another nest. Why workers would expend time and energy on colonies that are not their own has long been a “paradox for our understanding of social evolution and behavior,” Sumner says.
METHOD: As a PhD student studying hover wasps in the Malaysian jungle, Sumner had kept track of each individual in a nest (which usually number around 10) by painting colored marks on their backs. But in Panama, that tagging method proved inadequate for keeping tabs on the wandering paper wasps. So she turned to radio frequency identification (RFID), a technology that uses radio waves to wirelessly track tagged objects. Sumner found that more than 50 percent of the female wasps in any given colony of the paper wasp Polistes canadensis spent time working on other nests.1 Genetic testing revealed that wasps were visiting other colonies that were, in fact, genetically related. “That study was the first to use RFID technology in the field,” says longtime friend Mark Brown, a senior lecturer at Royal Holloway, University of London, who also studies social insects. “It illuminated a behavior that hadn’t been understood and opened a new realm of questions about the biology of social insects.”
RESULTS: Before working with paper wasps, Sumner spent several grueling months digging out leaf-cutter ant nests in Panama for her postdoctoral research at the University of Copenhagen. Building upon the work of her advisor, Koos Boomsma—who had discovered a parasitic ant species, Acromyrmex insinuator, secretly living among closely related leaf-cutter ants in the latter’s colonies—Sumner found that the intruders had a worker caste of their own, but, unlike the queens of the leaf-cutter ants they had evolved from, their queen mated with a single male.2 A. insinuator, which is indistinguishable from a leaf-cutter ant to the untrained eye, provides a fascinating model for studying unique social behaviors because it is still “in a very incipient stage of evolving into a parasite,” according to Sumner.
DISCUSSION: “Seirian has a remarkable skill of communicating science to an audience in a fun and easy-to-understand way,” says biodiversity scientist and Institute of Zoology colleague Kate Jones. Earlier this year, Sumner published a paper adapted from a series of innovative public outreach sessions with the goal of demonstrating the complexity of insect society. During these sessions, Sumner coaxed the audience into behaving like foraging leaf-cutter ants and monitored them using RFID. She found that when asked to “feed” from randomly placed buckets filled with varying qualities of food, humans proved significantly worse than ants at spotting high-quality food sources, as expected.3 And she also learned that the best predictor of efficient foraging in humans was not the use of verbal communication, but increased gesturing such as hand waving and pointing. “So even in humans, actions do speak louder than words,” Sumner says.
- S. Sumner et al., “Radio-tagging technology reveals extreme nest drifting in a eusocial insect,” Current Biology, 17:140-45, 2007. (Cited 29 times)
- S. Sumner et al., “Ant parasite queens revert to mating singly,” Nature, 428:35- 36, 2004. (Cited 45 times)
- A. J. King et al., “Performance of human groups in social foraging: the role of communication in consensus decision making,” Biology Letters, 7:237-40, 2011.