In this handout picture taken in 2016 at the lab at the Institute of Science and Technology Austria (ISTA) in Klosterneuburg, adult worker ants kill a terminally infected pupa inside its cocoon. Sick young ants release a smell that tells worker ants to destroy them to protect the colony from getting infected, scientists said Tuesday, adding that queens do not seem to commit act of self-sacrifice. (Photo by Christopher PULL / ISTA / AFP via Getty Images) / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO /CHRISTOPHER PULL/ INSTITUTE OF SCIENCE AND TECHNOLOGY AUSTRIA" - HANDOUT - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS