Blacklegged Tick Lifecycle (IMAGE) Cary Institute of Ecosystem Studies Caption This is a diagram of the blacklegged tick lifecycle. Infected nymphs pose the greatest threat to humans. Credit Leslie Tumblety Usage Restrictions To promote this press release. 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.