Parasitic Trematode Worms (IMAGE) University of California - San Diego Caption In parasitic trematode worm species, small members of the colony known as "soldiers" (left) are poised to attack any invading competing worms (right). In a new study, Resetarits and colleagues show that these worms can increase the number of soldiers in a colony in response to local invasion threat. Credit Image provided by Ryan Hechinger Usage Restrictions Image is only for use in media promoting this particular research study License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.