'Silent assassin Residents in Ontario, Canada, are warned to watch out for the toxic hammerhead worm, a non-native species .. According to the Hamilton Conservation Authority, hammerhead worms are a toxic, non-native species that first appeared in Ontario in 2017. They are believed to have arrived in North America via the introduction of plants from Southeast Asia.The term hammerhead worm encompasses various species of flatworms, also known as shovel-headed garden worms, which is a fitting description of their shape. They can grow between 5 and 10 centimeters in length and may exhibit multiple colors.They are also toxic, releasing a neurotoxin...