What you need to know about invasive hammerhead flatworms Pets could feel sick for a few days if they eat the invasive species and people could develop a minor rash if you touch them. Author: Taheshah Moise Updated: 3:06 PM CDT July 7, 2021 TEMPLE, Texas — Some call it the stuff of nightmares: dangerous worms that reproduce when they're cut instead of dying. We are talking about hammerhead flatworms. The invasive species is now in our area. Ashley Morgan-Olvera with the Texas Invasive Species Institute said hammerhead flatworms sometimes get mistaken for a baby snake because they can range in size from 8 inches to 15 inches. It's the shape of the head is what sets it apart.